diff --git a/.github/workflows/build_test.yaml b/.github/workflows/build_test.yaml
index 43b5370..e707e65 100644
--- a/.github/workflows/build_test.yaml
+++ b/.github/workflows/build_test.yaml
@@ -30,10 +30,12 @@ jobs:
       - name: Check code style
         run: |
           python3 -m pycodestyle ./lglpy
+          python3 -m pycodestyle ./generator
 
       - name: Check typing
         run: |
           python3 -m mypy ./lglpy
+          python3 -m mypy ./generator
 
   build-ubuntu-x64-clang:
     name: Ubuntu x64 Clang
diff --git a/generator/generate_vulkan_common.py b/generator/generate_vulkan_common.py
index fc18509..07d6976 100644
--- a/generator/generate_vulkan_common.py
+++ b/generator/generate_vulkan_common.py
@@ -28,10 +28,11 @@
 from datetime import datetime
 import os
 import re
-import shutil
 import sys
+from typing import Optional, TextIO
 import xml.etree.ElementTree as ET
 
+
 # These functions are not part of the layer implementation
 EXCLUDED_FUNCTIONS = {
     # Functions exposed by loader not the implementation
@@ -114,7 +115,8 @@
     'VkQueue',
 }
 
-class VersionMapping(dict):
+
+class VersionInfo(dict):
     '''
     Create a mapping of function => required version.
 
@@ -126,21 +128,24 @@ class VersionMapping(dict):
     possible extensions.
     '''
 
-    def __init__(self, root):
+    def __init__(self, root: ET.Element):
         '''
         Load all functions that are defined in the XML.
+
+        Args:
+            root: The root of the Vulkan spec XML document.
         '''
         self.load_api_core_versions(root)
         self.load_api_extensions(root)
 
-    def load_api_core_versions(self, root):
+    def load_api_core_versions(self, root: ET.Element):
         '''
         Load all core API functions that should be added to the map.
         '''
         # Find all the formally supported API feature groups
         features = root.findall('.//feature')
         for feature in features:
-            # Omit commands that are specific to VulkanSC
+            # Omit commands that are only used in VulkanSC
             apis = feature.get('api', 'vulkan').split(',')
             if 'vulkan' not in apis:
                 continue
@@ -155,14 +160,18 @@ def load_api_core_versions(self, root):
                 assert fname not in self, fname
                 self[fname] = [(api_version, None)]
 
-    def load_api_extensions(self, root):
+    def load_api_extensions(self, root: ET.Element):
         '''
         Load all extension API functions that should be added to the map.
+
+        Args:
+            root: The root of the Vulkan spec XML document.
         '''
         # Find all the formally supported API feature groups
         extensions = root.findall('.//extension')
         for extension in extensions:
             ext_name = extension.get('name')
+            assert ext_name is not None
 
             # Omit extensions that are specific to VulkanSC
             apis = extension.get('supported', 'vulkan').split(',')
@@ -170,12 +179,14 @@ def load_api_extensions(self, root):
                 continue
 
             # Omit extensions that are not on the Android platform
-            platforms = extension.get('platform', None)
+            platform = extension.get('platform', None)
             is_android = True
-            if platforms:
-                platforms = platforms.split(',')
-                is_android = 'android' in platforms
+            platform_list = None
+            if platform:
+                platform_list = platform.split(',')
+                is_android = 'android' in platform_list
 
+            # TODO: Relax this and allow other operating systems
             if not is_android:
                 continue
 
@@ -195,15 +206,18 @@ def load_api_extensions(self, root):
                 if fname not in self:
                     self[fname] = []
 
-                self[fname].append((ext_name, platforms))
+                self[fname].append((ext_name, platform_list))
 
-    def get_platform_define(self, command):
+    def get_platform_define(self, command: str) -> Optional[str]:
         '''
-        Determine the platform define for a command mapping.
+        Determine the platform define needed for a command mapping.
+
+        Args:
+            command: The name of the command to process.
         '''
         mappings = self[command]
 
-        platforms = set()
+        platforms = set()  # type: set[str]
 
         for mapping in mappings:
             # No platform always takes precedence
@@ -225,8 +239,32 @@ def get_platform_define(self, command):
 
 
 class Command:
+    '''
+    Parsed specification of a single Vulkan API entry point.
+
+    Attributes:
+        name: Name of this command.
+        dispatch_type: Is this 'instance' or 'device' for dispatch?
+        rtype: Function return type.
+        params: Function parameter list.
+        alias: Optional alias that provides the actual specification. For
+           commands with an alias, the dispatch_type, return type, and params
+           will be None until the alias is resolved.
+    '''
+
+    def __init__(self, mapping: VersionInfo, root: ET.Element):
+        '''
+        Create a new parsed Vulkan command entry.
+
+        Args:
+            mapping: The version information for that added this command.
+            root: The XML node root for the command subtree.
+        '''
+        self.alias = None
+        self.rtype = None
+        self.params = None
+        self.dispatch_type = None
 
-    def __init__(self, mapping, root):
         # Omit commands that are specific to VulkanSC
         apis = root.get('api', 'vulkan').split(',')
         if 'vulkan' not in apis:
@@ -235,12 +273,13 @@ def __init__(self, mapping, root):
         # Function is an alias
         if len(root) == 0:
             self.name = root.get('name')
+            assert self.name is not None
+
             self.alias = root.get('alias')
+            assert self.alias is not None
 
         # Function is a standalone specification
         else:
-            self.alias = None
-
             # Extract the basic function prototype
             proto = root[0]
             text = proto.text.strip() if proto.text else ''
@@ -250,6 +289,7 @@ def __init__(self, mapping, root):
             assert text == '' and tail == '', f'`{text}`, `{tail}`'
 
             rtype = proto[0]
+            assert rtype.text
             text = rtype.text.strip()
             tail = rtype.tail.strip() if rtype.tail else ''
             assert rtype.tag == 'type', ET.tostring(proto)
@@ -257,6 +297,7 @@ def __init__(self, mapping, root):
             self.rtype = text
 
             fname = proto[1]
+            assert fname.text
             text = fname.text.strip()
             tail = fname.tail.strip() if fname.tail else ''
             assert fname.tag == 'name', ET.tostring(proto)
@@ -281,8 +322,9 @@ def __init__(self, mapping, root):
 
                 type_prefix = f'{text} ' if text else ''
 
-                ptype = node[0]
                 valid_tail = ('', '*', '**', '* const*')
+                ptype = node[0]
+                assert ptype.text
                 text = ptype.text.strip()
                 tail = ptype.tail.strip() if ptype.tail else ''
                 assert ptype.tag == 'type', ET.tostring(proto)
@@ -290,16 +332,17 @@ def __init__(self, mapping, root):
 
                 type_postfix = f'{tail}' if tail else ''
 
-                ptype = f'{type_prefix}{text}{type_postfix}'
+                ptype_str = f'{type_prefix}{text}{type_postfix}'
 
                 pname = node[1]
+                assert pname.text
                 text = pname.text.strip()
                 tail = pname.tail.strip() if pname.tail else ''
                 assert pname.tag == 'name', ET.tostring(proto)
                 assert text
                 assert tail == '' or re.match(r'^\[\d+]$', tail)
 
-                self.params.append((ptype, text, tail))
+                self.params.append((ptype_str, text, tail))
 
         # Filter out functions that are not dynamically dispatched
         if self.name in EXCLUDED_FUNCTIONS:
@@ -311,19 +354,27 @@ def __init__(self, mapping, root):
 
         # Identify instance vs device functions
         if not self.alias:
-            dispatch_type = self.params[0][0]
-            if dispatch_type in INSTANCE_FUNCTION_PARAM_TYPE:
+            disp_type = self.params[0][0]
+            if disp_type in INSTANCE_FUNCTION_PARAM_TYPE:
                 self.dispatch_type = 'instance'
-            elif dispatch_type in DEVICE_FUNCTION_PARAM_TYPE:
+            elif disp_type in DEVICE_FUNCTION_PARAM_TYPE:
                 self.dispatch_type = 'device'
+            elif self.name.startswith('vkEnumerateInstance'):
+                self.dispatch_type = 'instance'
             else:
-                if self.name.startswith('vkEnumerateInstance'):
-                    self.dispatch_type = 'instance'
-                else:
-                    assert False, f'Unknown dispatch: {dispatch_type} {self.name}'
+                assert False, f'Unknown dispatch: {disp_type} {self.name}'
+
+
+def load_template(path: str) -> str:
+    '''
+    Load a template from the generator template directory.
 
+    Args:
+        path: The file name in the template directory.
 
-def load_template(path):
+    Returns:
+        The loaded text template.
+    '''
     base_dir = os.path.dirname(__file__)
     template_file = os.path.join(base_dir, 'vk_codegen', path)
 
@@ -334,7 +385,13 @@ def load_template(path):
     return data
 
 
-def write_copyright_header(file):
+def write_copyright_header(file: TextIO) -> None:
+    '''
+    Write the standard license and copyright header to the file.
+
+    Args:
+        file: The file handle to write to.
+    '''
     data = load_template('header.txt')
 
     start_year = 2024
@@ -350,8 +407,16 @@ def write_copyright_header(file):
     file.write('\n')
 
 
-def generate_layer_instance_dispatch_table(file, mapping, commands):
+def generate_instance_dispatch_table(
+        file: TextIO, mapping: VersionInfo, commands: list[Command]) -> None:
+    '''
+    Generate the instance dispatch table.
 
+    Args:
+        file: The file to write.
+        mapping: The version mapping information for the commands.
+        commands: The list of commands read from the spec.
+    '''
     # Write the copyright header to the file
     write_copyright_header(file)
 
@@ -367,29 +432,30 @@ def generate_layer_instance_dispatch_table(file, mapping, commands):
         if command.dispatch_type != 'instance':
             continue
 
-        tname = command.name
-        if tname in NO_INTERCEPT_OR_DISPATCH_FUNCTIONS:
+        assert command.name
+
+        if command.name in NO_INTERCEPT_OR_DISPATCH_FUNCTIONS:
             continue
 
         plat_define = mapping.get_platform_define(command.name)
 
         ttype = f'PFN_{command.name}'
 
-        if tname not in NO_INTERCEPT_FUNCTIONS:
+        if command.name not in NO_INTERCEPT_FUNCTIONS:
             if plat_define:
                 itable_members.append(f'#if defined({plat_define})')
 
-            itable_members.append(f'    ENTRY({tname}),')
+            itable_members.append(f'    ENTRY({command.name}),')
             if plat_define:
                 itable_members.append('#endif')
 
-        if tname not in NO_DISPATCH_FUNCTIONS:
+        if command.name not in NO_DISPATCH_FUNCTIONS:
             if plat_define:
                 dispatch_table_members.append(f'#if defined({plat_define})')
                 dispatch_table_inits.append(f'#if defined({plat_define})')
 
-            dispatch_table_members.append(f'    {ttype} {tname};')
-            dispatch_table_inits.append(f'    ENTRY({tname});')
+            dispatch_table_members.append(f'    {ttype} {command.name};')
+            dispatch_table_inits.append(f'    ENTRY({command.name});')
 
             if plat_define:
                 dispatch_table_members.append('#endif')
@@ -401,14 +467,14 @@ def generate_layer_instance_dispatch_table(file, mapping, commands):
         if command.dispatch_type != 'device':
             continue
 
+        assert command.name
         plat_define = mapping.get_platform_define(command.name)
         ttype = f'PFN_{command.name}'
-        tname = command.name
 
         if plat_define:
             itable_members.append(f'#if defined({plat_define})')
 
-        itable_members.append(f'    ENTRY({tname}),')
+        itable_members.append(f'    ENTRY({command.name}),')
 
         if plat_define:
             itable_members.append('#endif')
@@ -419,8 +485,16 @@ def generate_layer_instance_dispatch_table(file, mapping, commands):
     file.write(data)
 
 
-def generate_layer_instance_layer_decls(file, mapping, commands):
+def generate_instance_decls(
+        file: TextIO, mapping: VersionInfo, commands: list[Command]) -> None:
+    '''
+    Generate the instance intercept declarations header.
 
+    Args:
+        file: The file to write.
+        mapping: The version mapping information for the commands.
+        commands: The list of commands read from the spec.
+    '''
     # Write the copyright header to the file
     write_copyright_header(file)
 
@@ -436,6 +510,7 @@ def generate_layer_instance_layer_decls(file, mapping, commands):
             continue
 
         lines = []
+        assert command.name
 
         plat_define = mapping.get_platform_define(command.name)
         if plat_define:
@@ -444,7 +519,8 @@ def generate_layer_instance_layer_decls(file, mapping, commands):
         # Declare the default implementation
         lines.append('/* See Vulkan API for documentation. */')
         lines.append('/* Default common code pass-through implementation. */')
-        decl = f'VKAPI_ATTR {command.rtype} VKAPI_CALL layer_{command.name}_default('
+        decl = f'VKAPI_ATTR {command.rtype} ' \
+               f'VKAPI_CALL layer_{command.name}_default('
         lines.append(decl)
 
         for i, (ptype, pname, array) in enumerate(command.params):
@@ -482,8 +558,16 @@ def generate_layer_instance_layer_decls(file, mapping, commands):
         file.write('\n')
 
 
-def generate_layer_instance_layer_defs(file, mapping, commands):
+def generate_instance_defs(
+        file: TextIO, mapping: VersionInfo, commands: list[Command]) -> None:
+    '''
+    Generate the instance intercept definitions.
 
+    Args:
+        file: The file to write.
+        mapping: The version mapping information for the commands.
+        commands: The list of commands read from the spec.
+    '''
     # Write the copyright header to the file
     write_copyright_header(file)
 
@@ -495,11 +579,11 @@ def generate_layer_instance_layer_defs(file, mapping, commands):
         if command.dispatch_type != 'instance':
             continue
 
-        tname = command.name
-        if tname in NO_INTERCEPT_FUNCTIONS:
+        assert command.name
+        if command.name in NO_INTERCEPT_FUNCTIONS:
             continue
 
-        if tname in CUSTOM_FUNCTIONS:
+        if command.name in CUSTOM_FUNCTIONS:
             continue
 
         plat_define = mapping.get_platform_define(command.name)
@@ -507,7 +591,8 @@ def generate_layer_instance_layer_defs(file, mapping, commands):
             lines.append(f'#if defined({plat_define})\n')
 
         lines.append('/* See Vulkan API for documentation. */')
-        decl = f'VKAPI_ATTR {command.rtype} VKAPI_CALL layer_{command.name}_default('
+        decl = f'VKAPI_ATTR {command.rtype} ' \
+               f'VKAPI_CALL layer_{command.name}_default('
         lines.append(decl)
 
         for i, (ptype, pname, array) in enumerate(command.params):
@@ -541,8 +626,16 @@ def generate_layer_instance_layer_defs(file, mapping, commands):
     file.write(data)
 
 
-def generate_layer_device_dispatch_table(file, mapping, commands):
+def generate_device_dispatch_table(
+        file: TextIO, mapping: VersionInfo, commands: list[Command]) -> None:
+    '''
+    Generate the device dispatch table.
 
+    Args:
+        file: The file to write.
+        mapping: The version mapping information for the commands.
+        commands: The list of commands read from the spec.
+    '''
     # Write the copyright header to the file
     write_copyright_header(file)
 
@@ -552,12 +645,13 @@ def generate_layer_device_dispatch_table(file, mapping, commands):
     itable_members = []
     dispatch_table_members = []
     dispatch_table_inits = []
+
     for command in commands:
         if command.dispatch_type != 'device':
             continue
 
-        tname = command.name
-        if tname in NO_INTERCEPT_OR_DISPATCH_FUNCTIONS:
+        assert command.name
+        if command.name in NO_INTERCEPT_OR_DISPATCH_FUNCTIONS:
             continue
 
         plat_define = mapping.get_platform_define(command.name)
@@ -568,9 +662,9 @@ def generate_layer_device_dispatch_table(file, mapping, commands):
             dispatch_table_members.append(f'#if defined({plat_define})')
             dispatch_table_inits.append(f'#if defined({plat_define})')
 
-        itable_members.append(f'    ENTRY({tname}),')
-        dispatch_table_members.append(f'    {ttype} {tname};')
-        dispatch_table_inits.append(f'    ENTRY({tname});')
+        itable_members.append(f'    ENTRY({command.name}),')
+        dispatch_table_members.append(f'    {ttype} {command.name};')
+        dispatch_table_inits.append(f'    ENTRY({command.name});')
 
         if plat_define:
             itable_members.append('#endif')
@@ -583,7 +677,16 @@ def generate_layer_device_dispatch_table(file, mapping, commands):
     file.write(data)
 
 
-def generate_layer_device_layer_decls(file, mapping, commands):
+def generate_device_decls(
+        file: TextIO, mapping: VersionInfo, commands: list[Command]) -> None:
+    '''
+    Generate the device intercept declarations header.
+
+    Args:
+        file: The file to write.
+        mapping: The version mapping information for the commands.
+        commands: The list of commands read from the spec.
+    '''
 
     # Write the copyright header to the file
     write_copyright_header(file)
@@ -599,15 +702,17 @@ def generate_layer_device_layer_decls(file, mapping, commands):
         if command.dispatch_type != 'device':
             continue
 
-        lines = []
+        assert command.name
 
+        lines = []
         plat_define = mapping.get_platform_define(command.name)
         if plat_define:
             lines.append(f'#if defined({plat_define})\n')
 
         lines.append('/* See Vulkan API for documentation. */')
         lines.append('/* Default common code pass-through implementation. */')
-        decl = f'VKAPI_ATTR {command.rtype} VKAPI_CALL layer_{command.name}_default('
+        decl = f'VKAPI_ATTR {command.rtype} ' \
+               f'VKAPI_CALL layer_{command.name}_default('
         lines.append(decl)
 
         for i, (ptype, pname, array) in enumerate(command.params):
@@ -645,8 +750,16 @@ def generate_layer_device_layer_decls(file, mapping, commands):
         file.write('\n')
 
 
-def generate_layer_device_layer_defs(file, mapping, commands):
+def generate_device_defs(
+        file: TextIO, mapping: VersionInfo, commands: list[Command]) -> None:
+    '''
+    Generate the device intercept definitions.
 
+    Args:
+        file: The file to write.
+        mapping: The version mapping information for the commands.
+        commands: The list of commands read from the spec.
+    '''
     # Write the copyright header to the file
     write_copyright_header(file)
 
@@ -658,8 +771,8 @@ def generate_layer_device_layer_defs(file, mapping, commands):
         if command.dispatch_type != 'device':
             continue
 
-        tname = command.name
-        if tname in CUSTOM_FUNCTIONS:
+        assert command.name
+        if command.name in CUSTOM_FUNCTIONS:
             continue
 
         plat_define = mapping.get_platform_define(command.name)
@@ -668,7 +781,8 @@ def generate_layer_device_layer_defs(file, mapping, commands):
 
         lines.append('/* See Vulkan API for documentation. */')
 
-        decl = f'VKAPI_ATTR {command.rtype} VKAPI_CALL layer_{command.name}_default('
+        decl = f'VKAPI_ATTR {command.rtype} ' \
+               f'VKAPI_CALL layer_{command.name}_default('
         lines.append(decl)
 
         for i, (ptype, pname, array) in enumerate(command.params):
@@ -702,13 +816,7 @@ def generate_layer_device_layer_defs(file, mapping, commands):
     file.write(data)
 
 
-def copy_resource(src_dir, out_dir):
-    out_dir = os.path.abspath(out_dir)
-    os.makedirs(out_dir, exist_ok=True)
-    shutil.copytree(src_dir, out_dir, dirs_exist_ok=True)
-
-
-def main():
+def main() -> int:
     '''
     Tool main function.
 
@@ -724,7 +832,7 @@ def main():
     root = tree.getroot()
 
     # Parse function to API version or extension mapping
-    mapping = VersionMapping(root)
+    mapping = VersionInfo(root)
 
     # Parse function prototypes
     nodes = root.findall('.//commands/command')
@@ -748,36 +856,33 @@ def main():
             command.params = aliases[0].params
             command.dispatch_type = aliases[0].dispatch_type
 
-        # Remove the alias to avoid confusion in future
-        del command.alias
-
     # Sort functions into alphabetical order
-    commands.sort(key=lambda x: x.name)
+    commands.sort(key=lambda x: str(x.name))
 
     # Generate dynamic resources
     outfile = os.path.join(outdir, 'instance_dispatch_table.hpp')
     with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_instance_dispatch_table(handle, mapping, commands)
-
-    outfile = os.path.join(outdir, 'device_dispatch_table.hpp')
-    with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_device_dispatch_table(handle, mapping, commands)
+        generate_instance_dispatch_table(handle, mapping, commands)
 
     outfile = os.path.join(outdir, 'instance_functions.hpp')
     with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_instance_layer_decls(handle, mapping, commands)
+        generate_instance_decls(handle, mapping, commands)
 
     outfile = os.path.join(outdir, 'instance_functions.cpp')
     with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_instance_layer_defs(handle, mapping, commands)
+        generate_instance_defs(handle, mapping, commands)
+
+    outfile = os.path.join(outdir, 'device_dispatch_table.hpp')
+    with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
+        generate_device_dispatch_table(handle, mapping, commands)
 
     outfile = os.path.join(outdir, 'device_functions.hpp')
     with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_device_layer_decls(handle, mapping, commands)
+        generate_device_decls(handle, mapping, commands)
 
     outfile = os.path.join(outdir, 'device_functions.cpp')
     with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_device_layer_defs(handle, mapping, commands)
+        generate_device_defs(handle, mapping, commands)
 
     return 0
 
diff --git a/generator/generate_vulkan_layer.py b/generator/generate_vulkan_layer.py
index d833fe5..8242423 100644
--- a/generator/generate_vulkan_layer.py
+++ b/generator/generate_vulkan_layer.py
@@ -26,284 +26,23 @@
 '''
 
 import argparse
-from datetime import datetime
 import os
 import re
 import shutil
 import sys
-import xml.etree.ElementTree as ET
-
-# These functions are manually created as fully exported entry points in the
-# layer library, and are not part of the dynamic dispatch behavior
-MANUAL_FUNCTIONS = {
-    # Exposed by loader so not handled by the layer
-    'vkEnumerateInstanceVersion',
-    # Exposed as symbols managed by the loader so not handled by the layer
-    'vkGetInstanceProcAddr',
-    'vkGetDeviceProcAddr',
-    # Exposed by layer as explicit entry points
-    'vkEnumerateDeviceLayerProperties',
-    'vkEnumerateInstanceExtensionProperties',
-    'vkEnumerateInstanceLayerProperties',
-}
-
-# These functions are manually exported, but we can use driver forwarding
-FORWARD_WITHOUT_INTERCEPT = {
-    'vkEnumerateDeviceExtensionProperties',
-    'vkEnumerateInstanceExtensionProperties',
-}
-
-# These functions are found via the loader-injected chain info
-INTERCEPT_WITHOUT_FORWARD = {
-    'vkCreateDevice',
-    'vkCreateInstance',
-}
-
-# Filter out extensions from these vendors by default
-EXTENSION_VENDOR_FILTER = {
-    'AMD',
-    'ANDROID',
-    'GOOGLE',
-    'HUAWEI',
-    'IMG',
-    'INTEL',
-    'LUNARG',
-    'MSFT',
-    'NV',
-    'NVX',
-    'QCOM',
-    'SEC',
-    'VALVE',
-}
-
-# Filter out KHR and EXT extensions that we don't support or need on Android
-EXTENSION_NAME_FILTER = {
-    'VK_KHR_video_queue',
-    'VK_KHR_video_decode_queue',
-    'VK_KHR_video_encode_queue',
-    'VK_EXT_acquire_drm_display',
-    'VK_EXT_headless_surface',
-}
-
-INSTANCE_FUNCTION_PARAM_TYPE = {
-    'const VkInstanceCreateInfo*',
-    'VkInstance',
-    'VkPhysicalDevice',
-}
-
-DEVICE_FUNCTION_PARAM_TYPE = {
-    'VkCommandBuffer',
-    'VkDevice',
-    'VkQueue',
-}
-
-class VersionMapping(dict):
-    '''
-    Create a mapping of function => required version.
+from typing import TextIO
 
-    The required version is a list of either:
-      * An API version string ('1.0', '1.1', etc)
-      * An extension string (e.g. 'VK_KHR_swapchain')
 
-    The required version is a list because some APIs can be added by multiple
-    possible extensions.
+def load_template(path: str) -> str:
     '''
+    Load a template from the generator template directory.
+
+    Args:
+        path: The file name in the template directory.
 
-    def __init__(self, root):
-        '''
-        Load all functions that are defined in the XML.
-        '''
-        self.load_api_core_versions(root)
-        self.load_api_extensions(root)
-
-    def load_api_core_versions(self, root):
-        '''
-        Load all core API functions that should be added to the map.
-        '''
-        # Find all the formally supported API feature groups
-        features = root.findall('.//feature')
-        for feature in features:
-            # Omit commands that are specific to VulkanSC
-            apis = feature.get('api', 'vulkan').split(',')
-            if 'vulkan' not in apis:
-                continue
-
-            # Get the API version
-            api_version = feature.get('number')
-
-            # Get the commands added in this API version
-            commands = feature.findall('.//command')
-            for command in commands:
-                fname = command.get('name')
-                assert fname not in self, fname
-                self[fname] = [(api_version, None)]
-
-    def load_api_extensions(self, root):
-        '''
-        Load all extension API functions that should be added to the map.
-        '''
-        # Find all the formally supported API feature groups
-        extensions = root.findall('.//extension')
-        for extension in extensions:
-            ext_name = extension.get('name')
-
-            # Omit extensions that are specific to VulkanSC
-            apis = extension.get('supported', 'vulkan').split(',')
-            if 'vulkan' not in apis:
-                continue
-
-            # Omit extensions that are not on the Android platform
-            platforms = extension.get('platform', None)
-            is_android = True
-            if platforms:
-                platforms = platforms.split(',')
-                is_android = 'android' in platforms
-
-            if not is_android:
-                continue
-
-            # Omit extensions that are from other vendors
-            vendor = ext_name.split("_")[1]
-            if vendor in EXTENSION_VENDOR_FILTER:
-                continue
-
-            # Omit extensions that are explicitly not supported e.g. video
-            if ext_name in EXTENSION_NAME_FILTER:
-                continue
-
-            # Note, not all extensions have commands
-            commands = extension.findall('.//command')
-            for command in commands:
-                fname = command.get('name')
-                if fname not in self:
-                    self[fname] = []
-
-                self[fname].append((ext_name, platforms))
-
-    def get_platform_define(self, command):
-        '''
-        Determine the platform define for a command mapping.
-        '''
-        mappings = self[command]
-
-        platforms = set()
-
-        for mapping in mappings:
-            # No platform always takes precedence
-            if mapping[1] is None:
-                platforms = set()
-                break
-
-            # Limited platforms accumulate
-            platforms.update(set(mapping[1]))
-
-        # Currently only handle no define mapping or Android only
-        if not platforms:
-            return None
-
-        if len(platforms) == 1 and 'android' in platforms:
-            return 'VK_USE_PLATFORM_ANDROID_KHR'
-
-        assert False, f'Unhandled mapping: {platforms}'
-
-
-class Command:
-
-    def __init__(self, mapping, root):
-        # Omit commands that are specific to VulkanSC
-        apis = root.get('api', 'vulkan').split(',')
-        if 'vulkan' not in apis:
-            raise NotImplementedError
-
-        # Function is an alias
-        if len(root) == 0:
-            self.name = root.get('name')
-            self.alias = root.get('alias')
-
-        # Function is a standalone specification
-        else:
-            self.alias = None
-
-            # Extract the basic function prototype
-            proto = root[0]
-            text = proto.text.strip() if proto.text else ''
-            tail = proto.tail.strip() if proto.tail else ''
-            assert proto.tag == 'proto', ET.tostring(proto)
-            assert len(proto) == 2, ET.tostring(proto)
-            assert text == '' and tail == '', f'`{text}`, `{tail}`'
-
-            rtype = proto[0]
-            text = rtype.text.strip()
-            tail = rtype.tail.strip() if rtype.tail else ''
-            assert rtype.tag == 'type', ET.tostring(proto)
-            assert text and tail == '', f'`{text}`, `{tail}`'
-            self.rtype = text
-
-            fname = proto[1]
-            text = fname.text.strip()
-            tail = fname.tail.strip() if fname.tail else ''
-            assert fname.tag == 'name', ET.tostring(proto)
-            assert text and tail == '', f'`{text}`, `{tail}`'
-            self.name = text
-            self.params = []
-
-            # Extract the function parameters
-            parameters = root.findall('./param')
-            for node in parameters:
-                assert len(node) == 2, ET.tostring(node)
-
-                # Omit parameters that are specific to VulkanSC
-                apis = node.get('api', 'vulkan').split(',')
-                if 'vulkan' not in apis:
-                    continue
-
-                valid_text = ('', 'const', 'struct', 'const struct')
-                text = node.text.strip() if node.text else ''
-                tail = node.tail.strip() if node.tail else ''
-                assert text in valid_text and tail == '', f'`{text}`, `{tail}`'
-
-                type_prefix = f'{text} ' if text else ''
-
-                ptype = node[0]
-                valid_tail = ('', '*', '**', '* const*')
-                text = ptype.text.strip()
-                tail = ptype.tail.strip() if ptype.tail else ''
-                assert ptype.tag == 'type', ET.tostring(proto)
-                assert text and tail in valid_tail, f'`{text}`, `{tail}`'
-
-                type_postfix = f'{tail}' if tail else ''
-
-                ptype = f'{type_prefix}{text}{type_postfix}'
-
-                pname = node[1]
-                text = pname.text.strip()
-                tail = pname.tail.strip() if pname.tail else ''
-                assert pname.tag == 'name', ET.tostring(proto)
-                assert text
-                assert tail == '' or re.match(r'^\[\d+]$', tail)
-
-                self.params.append((ptype, text, tail))
-
-        # Filter out functions that are not dynamically dispatched
-        if self.name in MANUAL_FUNCTIONS:
-            raise NotImplementedError
-
-        # Filter out functions that are not in our supported mapping
-        if self.name not in mapping:
-            raise NotImplementedError
-
-        # Identify instance vs device functions
-        if not self.alias:
-            dispatch_type = self.params[0][0]
-            if dispatch_type in INSTANCE_FUNCTION_PARAM_TYPE:
-                self.dispatch_type = 'instance'
-            elif dispatch_type in DEVICE_FUNCTION_PARAM_TYPE:
-                self.dispatch_type = 'device'
-            else:
-                assert False, f'Unknown dispatch: {dispatch_type} {self.name}'
-
-
-def load_template(path):
+    Returns:
+        The loaded text template.
+    '''
     base_dir = os.path.dirname(__file__)
     template_file = os.path.join(base_dir, 'vk_codegen', path)
 
@@ -314,75 +53,110 @@ def load_template(path):
     return data
 
 
-def write_copyright_header(file):
-    data = load_template('header.txt')
-
-    start_year = 2024
-    end_year = datetime.now().year
-    if start_year == end_year:
-        date_string = f'{start_year}'
-    else:
-        date_string = f'{start_year}-{end_year}'
+def get_layer_api_name(vendor: str, layer: str) -> str:
+    '''
+    Generate the layer string name for the new layer used by the loader.
+    Names are of the form "VK_LAYER_<VENDOR>_<LAYER>" in upper case.
 
-    data = data.replace('{COPYRIGHT_YEARS}', date_string)
+    Args:
+        vendor: The layer vendor tag.
+        layer: The name of the layer.
 
-    file.write(data)
-    file.write('\n')
+    Returns:
+        The layer string name used by the loader.
+    '''
+    pattern = re.compile(r'^VkLayer(\w+)$')
+    match = pattern.match(layer)
+    assert match
 
+    name_parts = ('VK_LAYER', vendor.upper(), match.group(1).upper())
+    return '_'.join(name_parts)
 
-def generate_layer_root_cmake(file, project_name, layer_name):
-    data = load_template('root_CMakeLists.txt')
-    data = data.replace('{PROJECT_NAME}', project_name)
-    data = data.replace('{LAYER_NAME}', layer_name)
-    file.write(data)
 
+def get_layer_api_description(vendor: str, layer: str) -> str:
+    '''
+    Generate the layer description placeholder to return from the layer
+    enumeration query in the API. We expect developers to replace this with
+    something more useful for long-lived layers.
 
-def get_layer_api_name(vendor_name, layer_name):
+    Args:
+        vendor: The layer vendor tag.
+        layer: The name of the layer.
 
-    pattern = re.compile(r'^VkLayer(\w+)$')
-    match = pattern.match(layer_name)
-    assert match
+    Returns:
+        The layer string description returned by the API queries.
+    '''
+    return f'{layer} by {vendor}'
 
-    name_parts = ('VK_LAYER', vendor_name.upper(), match.group(1).upper())
-    return '_'.join(name_parts)
 
+def generate_root_cmake(file: TextIO, project: str, layer: str) -> None:
+    '''
+    Generate the root CMake file for a new layer.
 
-def get_layer_api_description(vendor_name, layer_name):
-    return f'{layer_name} by {vendor_name}'
+    Args:
+        file: The file handle to write to.
+        project: The name of the CMake project.
+        layer: The name of the layer used as the Android log tag.
+    '''
+    data = load_template('root_CMakeLists.txt')
+    data = data.replace('{PROJECT_NAME}', project)
+    data = data.replace('{LAYER_NAME}', layer)
+    file.write(data)
 
 
-def generate_layer_source_cmake(file, vendor_name, layer_name):
+def generate_source_cmake(file: TextIO, vendor: str, layer: str) -> None:
+    '''
+    Generate the layer source directory CMake file for a new layer.
 
+    Args:
+        file: The file handle to write to.
+        vendor: The layer vendor tag.
+        layer: The name of the layer.
+    '''
     data = load_template('source_CMakeLists.txt')
-    data = data.replace('{LAYER_NAME}', layer_name)
+    data = data.replace('{LAYER_NAME}', layer)
 
-    name = get_layer_api_name(vendor_name, layer_name)
+    name = get_layer_api_name(vendor, layer)
     data = data.replace('{LGL_LAYER_NAME}', name)
 
-    desc = get_layer_api_description(vendor_name, layer_name)
+    desc = get_layer_api_description(vendor, layer)
     data = data.replace('{LGL_LAYER_DESC}', desc)
 
     file.write(data)
 
 
-def generate_layer_install_helper(file, vendor_name, layer_name):
+def generate_install_helper(file: TextIO, vendor: str, layer: str) -> None:
+    '''
+    Generate the Android installer helper with placeholders replaced.
 
+    Args:
+        file: The file handle to write to.
+        vendor: The layer vendor tag.
+        layer: The name of the layer.
+    '''
     data = load_template('android_install.py')
-    data = data.replace('{LAYER_NAME}', layer_name)
+    data = data.replace('{LAYER_NAME}', layer)
 
-    name = get_layer_api_name(vendor_name, layer_name)
+    name = get_layer_api_name(vendor, layer)
     data = data.replace('{LGL_LAYER_NAME}', name)
 
     file.write(data)
 
 
-def copy_resource(src_dir, out_dir):
-    out_dir = os.path.abspath(out_dir)
-    os.makedirs(out_dir, exist_ok=True)
-    shutil.copytree(src_dir, out_dir, dirs_exist_ok=True)
+def copy_resource(src_dir: str, dst_dir: str) -> None:
+    '''
+    Copy a directory of resources to another location.
+
+    Args:
+        src_dir: The source directory location.
+        out_dir: The destination directory location.
+    '''
+    dst_dir = os.path.abspath(dst_dir)
+    os.makedirs(dst_dir, exist_ok=True)
+    shutil.copytree(src_dir, dst_dir, dirs_exist_ok=True)
 
 
-def parse_command_line():
+def parse_command_line() -> argparse.Namespace:
     '''
     Parse the command line.
 
@@ -395,10 +169,10 @@ def parse_command_line():
                         help='CMake project name')
 
     parser.add_argument('--vendor-name', default='LGL',
-                        help='Layer vendor name (optional)')
+                        help='layer vendor name (optional)')
 
     parser.add_argument('--layer-name', default=None,
-                        help='Layer name (optional)')
+                        help='layer name (optional)')
 
     parser.add_argument('--output', metavar='DIR', required=True,
                         help='output directory for layer project')
@@ -414,7 +188,7 @@ def parse_command_line():
     return args
 
 
-def main():
+def main() -> int:
     '''
     Tool main function.
 
@@ -426,7 +200,7 @@ def main():
     # Validate the layer name is well formed
     pattern = re.compile(r'^VkLayer\w+$')
     if not pattern.match(args.layer_name):
-        print(f'ERROR: Layer name "{args.layer_name}" is invalid')
+        print(f'ERROR: Layer name "{args.layer_name}" must start with VkLayer')
         return 1
 
     # Check that output directory is either empty or over-writable
@@ -435,64 +209,31 @@ def main():
         if not os.path.isdir(outdir):
             print(f'ERROR: Output location "{outdir}" is not a directory')
             return 1
+
         if len(os.listdir(outdir)) != 0 and not args.overwrite:
             print(f'ERROR: Output directory "{outdir}" is not empty')
             return 1
 
-    # Parse the XML headers
-    tree = ET.parse('./khronos/vulkan/registry/vk.xml')
-    root = tree.getroot()
-
-    # Parse function to API version or extension mapping
-    mapping = VersionMapping(root)
-
-    # Parse function prototypes
-    nodes = root.findall('.//commands/command')
-
-    commands = []
-    for node in nodes:
-        # Parse, skipping commands for sibling APIs
-        try:
-            commands.append(Command(mapping, node))
-        except NotImplementedError:
-            pass
-
-    # Flatten out command alias cross-references
-    for command in commands:
-        alias_name = command.alias
-        if alias_name:
-            aliases = [x for x in commands if x.name == alias_name]
-            assert len(aliases) == 1
-
-            command.rtype = aliases[0].rtype
-            command.params = aliases[0].params
-            command.dispatch_type = aliases[0].dispatch_type
-
-        # Remove the alias to avoid confusion in future
-        del command.alias
-
-    # Sort functions into alphabetical order
-    commands.sort(key=lambda x: x.name)
-
     # Generate static resources
     base_dir = os.path.dirname(__file__)
     source_dir = os.path.join(base_dir, 'vk_layer')
     copy_resource(source_dir, outdir)
 
-    # Generate the layer skeleton
+    # Generate templated resources
     outfile = os.path.join(outdir, 'CMakeLists.txt')
     with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_root_cmake(handle, args.project_name, args.layer_name)
+        generate_root_cmake(handle, args.project_name, args.layer_name)
 
     outfile = os.path.join(outdir, 'source/CMakeLists.txt')
     with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_source_cmake(handle, args.vendor_name, args.layer_name)
+        generate_source_cmake(handle, args.vendor_name, args.layer_name)
 
     outfile = os.path.join(outdir, 'android_install.py')
     with open(outfile, 'w', encoding='utf-8', newline='\n') as handle:
-        generate_layer_install_helper(handle, args.vendor_name, args.layer_name)
+        generate_install_helper(handle, args.vendor_name, args.layer_name)
 
     return 0
 
+
 if __name__ == '__main__':
     sys.exit(main())
diff --git a/generator/vk_codegen/android_install.py b/generator/vk_codegen/android_install.py
index 1cd3d03..22d8ce0 100644
--- a/generator/vk_codegen/android_install.py
+++ b/generator/vk_codegen/android_install.py
@@ -30,6 +30,7 @@
 import shlex
 import subprocess as sp
 import sys
+from typing import Any, Optional
 
 # Android temp directory
 ANDROID_TMP_DIR = '/data/local/tmp/'
@@ -38,6 +39,7 @@
 EXPECTED_VULKAN_LAYER_NAME = '{LGL_LAYER_NAME}'
 EXPECTED_VULKAN_LAYER_FILE = 'lib{LAYER_NAME}.so'
 
+
 class Device:
     '''
     A basic wrapper around adb, allowing a specific device to be registered.
@@ -46,7 +48,7 @@ class Device:
         device: The name of the device to call, or None for non-specific use.
     '''
 
-    def adb_quiet(self, *args):
+    def adb_quiet(self, *args: str) -> None:
         '''
         Call `adb` to run a command, but ignore output and errors.
 
@@ -57,7 +59,7 @@ def adb_quiet(self, *args):
         commands.extend(args)
         sp.run(commands, stdout=sp.DEVNULL, stderr=sp.DEVNULL, check=False)
 
-    def adb(self, *args, **kwargs):
+    def adb(self, *args: str, **kwargs: Any) -> str:
         '''
         Call `adb` to run command, and capture output and results.
 
@@ -73,7 +75,7 @@ def adb(self, *args, **kwargs):
         Raises:
             CalledProcessError: The subprocess was not successfully executed.
         '''
-        commands = ['adb']
+        commands = ['adb']  # type: Any
         commands.extend(args)
 
         text = kwargs.get('text', True)
@@ -84,12 +86,12 @@ def adb(self, *args, **kwargs):
         if shell:
             # Unix shells need a flattened command for shell commands
             if os.name != 'nt':
-                quotedCommands = []
+                quoted_commands = []
                 for command in commands:
                     if command != '>':
                         command = shlex.quote(command)
-                    quotedCommands.append(command)
-                commands = ' '.join(quotedCommands)
+                    quoted_commands.append(command)
+                commands = ' '.join(quoted_commands)
 
         # Run on the device but with shell argument quoting
         if quote:
@@ -101,11 +103,13 @@ def adb(self, *args, **kwargs):
 
         return rep.stdout
 
-    def adb_run_as(self, package, *args, quiet=False):
+    def adb_run_as(self, package: str,
+                   *args: str, quiet: bool = False) -> Optional[str]:
         '''
         Call `adb` to run command as a package using `run-as` or as root,
         if root is accessible. If command will be run as root, this function
-        will change CWD to the package data directory before executing the command.
+        will change CWD to the package data directory before executing the
+        command.
 
         Args:
             package: Package name to run-as or change CWD to.
@@ -113,7 +117,7 @@ def adb_run_as(self, package, *args, quiet=False):
             quiet: If True, ignores output from adb.
 
         Returns:
-            The contents of stdout or Nothing, if quiet=True.
+            The contents of stdout or None if quiet=True.
 
         Raises:
             CalledProcessError: The subprocess was not successfully executed.
@@ -122,12 +126,14 @@ def adb_run_as(self, package, *args, quiet=False):
         command.extend(args)
 
         if quiet:
-            return self.adb_quiet(*command)
+            self.adb_quiet(*command)
+            return None
 
         return self.adb(*command)
 
 
-def enable_vulkan_debug_layer(device, package, layer):
+def enable_vulkan_debug_layer(
+        device: Device, package: str, layer: str) -> None:
     '''
     Args:
         device: The device instance.
@@ -138,16 +144,24 @@ def enable_vulkan_debug_layer(device, package, layer):
     print('\nInstalling Vulkan debug layer')
 
     layer = os.path.normpath(layer)
-    layerBase = os.path.basename(os.path.normpath(layer))
+    layer_base = os.path.basename(os.path.normpath(layer))
 
     device.adb('push', layer, ANDROID_TMP_DIR)
-    device.adb_run_as(package, 'cp', ANDROID_TMP_DIR + layerBase, '.')
-    device.adb('shell', 'settings', 'put', 'global', 'enable_gpu_debug_layers', '1')
-    device.adb('shell', 'settings', 'put', 'global', 'gpu_debug_app', package)
-    device.adb('shell', 'settings', 'put', 'global', 'gpu_debug_layers', EXPECTED_VULKAN_LAYER_NAME)
 
+    device.adb_run_as(package, 'cp', ANDROID_TMP_DIR + layer_base, '.')
+
+    device.adb('shell', 'settings', 'put', 'global',
+               'enable_gpu_debug_layers', '1')
+
+    device.adb('shell', 'settings', 'put', 'global',
+               'gpu_debug_app', package)
 
-def disable_vulkan_debug_layer(device, package, layer):
+    device.adb('shell', 'settings', 'put', 'global',
+               'gpu_debug_layers', EXPECTED_VULKAN_LAYER_NAME)
+
+
+def disable_vulkan_debug_layer(
+        device: Device, package: str, layer: str) -> None:
     '''
     Clean up the Vulkan layer installation.
 
@@ -157,35 +171,44 @@ def disable_vulkan_debug_layer(device, package, layer):
     '''
     print('\nRemoving Vulkan debug layer')
 
-    layerBase = os.path.basename(os.path.normpath(layer))
+    layer_base = os.path.basename(os.path.normpath(layer))
+
+    device.adb('shell', 'settings', 'delete', 'global',
+               'enable_gpu_debug_layers')
+
+    device.adb('shell', 'settings', 'delete', 'global',
+               'gpu_debug_app')
 
-    device.adb('shell', 'settings', 'delete', 'global', 'enable_gpu_debug_layers')
-    device.adb('shell', 'settings', 'delete', 'global gpu_debug_app')
-    device.adb('shell', 'settings', 'delete', 'global gpu_debug_layers')
-    device.adb_run_as(package, 'rm', layerBase, quiet=True)
+    device.adb('shell', 'settings', 'delete', 'global',
+               'gpu_debug_layers')
 
+    device.adb_run_as(package, 'rm', layer_base, quiet=True)
 
-def get_layer():
+
+def get_layer() -> Optional[str]:
     '''
     Find the debug layer to use in the build directory.
+
+    Returns:
+        The part to the library to use.
     '''
 
     base_dir = './build_arm64/source/'
 
-    sym_lib = None
+    # TODO: If we want to use symbolized layer we need to rename it
     lib = None
 
     for path in os.listdir(base_dir):
+        # Match symbolized library first so we don't use it
         if path.endswith('_sym.so'):
-            sym_lib = os.path.join(base_dir, path)
+            _ = os.path.join(base_dir, path)
         elif path.endswith('.so'):
             lib = os.path.join(base_dir, path)
 
-    # TODO: If we want to use symbolized layer we need to rename it
     return lib
 
 
-def parse_command_line():
+def parse_command_line() -> argparse.Namespace:
     '''
     Parse the command line.
 
@@ -200,7 +223,7 @@ def parse_command_line():
     return parser.parse_args()
 
 
-def main():
+def main() -> int:
     '''
     Script main function.
 
@@ -211,6 +234,9 @@ def main():
 
     device = Device()
     layer = get_layer()
+    if not layer:
+        print('ERROR: Layer binary not found')
+        return 1
 
     enable_vulkan_debug_layer(device, args.package, layer)
 
@@ -218,6 +244,9 @@ def main():
 
     disable_vulkan_debug_layer(device, args.package, layer)
 
+    return 0
+
+
 if __name__ == '__main__':
     try:
         sys.exit(main())
diff --git a/layer_example/android_install.py b/layer_example/android_install.py
index 7ae37eb..a8a300f 100644
--- a/layer_example/android_install.py
+++ b/layer_example/android_install.py
@@ -30,6 +30,7 @@
 import shlex
 import subprocess as sp
 import sys
+from typing import Any, Optional
 
 # Android temp directory
 ANDROID_TMP_DIR = '/data/local/tmp/'
@@ -38,6 +39,7 @@
 EXPECTED_VULKAN_LAYER_NAME = 'VK_LAYER_LGL_EXAMPLE'
 EXPECTED_VULKAN_LAYER_FILE = 'libVkLayerExample.so'
 
+
 class Device:
     '''
     A basic wrapper around adb, allowing a specific device to be registered.
@@ -46,7 +48,7 @@ class Device:
         device: The name of the device to call, or None for non-specific use.
     '''
 
-    def adb_quiet(self, *args):
+    def adb_quiet(self, *args: str) -> None:
         '''
         Call `adb` to run a command, but ignore output and errors.
 
@@ -57,7 +59,7 @@ def adb_quiet(self, *args):
         commands.extend(args)
         sp.run(commands, stdout=sp.DEVNULL, stderr=sp.DEVNULL, check=False)
 
-    def adb(self, *args, **kwargs):
+    def adb(self, *args: str, **kwargs: Any) -> str:
         '''
         Call `adb` to run command, and capture output and results.
 
@@ -73,7 +75,7 @@ def adb(self, *args, **kwargs):
         Raises:
             CalledProcessError: The subprocess was not successfully executed.
         '''
-        commands = ['adb']
+        commands = ['adb']  # type: Any
         commands.extend(args)
 
         text = kwargs.get('text', True)
@@ -84,12 +86,12 @@ def adb(self, *args, **kwargs):
         if shell:
             # Unix shells need a flattened command for shell commands
             if os.name != 'nt':
-                quotedCommands = []
+                quoted_commands = []
                 for command in commands:
                     if command != '>':
                         command = shlex.quote(command)
-                    quotedCommands.append(command)
-                commands = ' '.join(quotedCommands)
+                    quoted_commands.append(command)
+                commands = ' '.join(quoted_commands)
 
         # Run on the device but with shell argument quoting
         if quote:
@@ -101,11 +103,13 @@ def adb(self, *args, **kwargs):
 
         return rep.stdout
 
-    def adb_run_as(self, package, *args, quiet=False):
+    def adb_run_as(self, package: str,
+                   *args: str, quiet: bool = False) -> Optional[str]:
         '''
         Call `adb` to run command as a package using `run-as` or as root,
         if root is accessible. If command will be run as root, this function
-        will change CWD to the package data directory before executing the command.
+        will change CWD to the package data directory before executing the
+        command.
 
         Args:
             package: Package name to run-as or change CWD to.
@@ -113,7 +117,7 @@ def adb_run_as(self, package, *args, quiet=False):
             quiet: If True, ignores output from adb.
 
         Returns:
-            The contents of stdout or Nothing, if quiet=True.
+            The contents of stdout or None if quiet=True.
 
         Raises:
             CalledProcessError: The subprocess was not successfully executed.
@@ -122,12 +126,14 @@ def adb_run_as(self, package, *args, quiet=False):
         command.extend(args)
 
         if quiet:
-            return self.adb_quiet(*command)
+            self.adb_quiet(*command)
+            return None
 
         return self.adb(*command)
 
 
-def enable_vulkan_debug_layer(device, package, layer):
+def enable_vulkan_debug_layer(
+        device: Device, package: str, layer: str) -> None:
     '''
     Args:
         device: The device instance.
@@ -138,16 +144,24 @@ def enable_vulkan_debug_layer(device, package, layer):
     print('\nInstalling Vulkan debug layer')
 
     layer = os.path.normpath(layer)
-    layerBase = os.path.basename(os.path.normpath(layer))
+    layer_base = os.path.basename(os.path.normpath(layer))
 
     device.adb('push', layer, ANDROID_TMP_DIR)
-    device.adb_run_as(package, 'cp', ANDROID_TMP_DIR + layerBase, '.')
-    device.adb('shell', 'settings', 'put', 'global', 'enable_gpu_debug_layers', '1')
-    device.adb('shell', 'settings', 'put', 'global', 'gpu_debug_app', package)
-    device.adb('shell', 'settings', 'put', 'global', 'gpu_debug_layers', EXPECTED_VULKAN_LAYER_NAME)
 
+    device.adb_run_as(package, 'cp', ANDROID_TMP_DIR + layer_base, '.')
+
+    device.adb('shell', 'settings', 'put', 'global',
+               'enable_gpu_debug_layers', '1')
+
+    device.adb('shell', 'settings', 'put', 'global',
+               'gpu_debug_app', package)
 
-def disable_vulkan_debug_layer(device, package, layer):
+    device.adb('shell', 'settings', 'put', 'global',
+               'gpu_debug_layers', EXPECTED_VULKAN_LAYER_NAME)
+
+
+def disable_vulkan_debug_layer(
+        device: Device, package: str, layer: str) -> None:
     '''
     Clean up the Vulkan layer installation.
 
@@ -157,35 +171,44 @@ def disable_vulkan_debug_layer(device, package, layer):
     '''
     print('\nRemoving Vulkan debug layer')
 
-    layerBase = os.path.basename(os.path.normpath(layer))
+    layer_base = os.path.basename(os.path.normpath(layer))
+
+    device.adb('shell', 'settings', 'delete', 'global',
+               'enable_gpu_debug_layers')
+
+    device.adb('shell', 'settings', 'delete', 'global',
+               'gpu_debug_app')
 
-    device.adb('shell', 'settings', 'delete', 'global', 'enable_gpu_debug_layers')
-    device.adb('shell', 'settings', 'delete', 'global gpu_debug_app')
-    device.adb('shell', 'settings', 'delete', 'global gpu_debug_layers')
-    device.adb_run_as(package, 'rm', layerBase, quiet=True)
+    device.adb('shell', 'settings', 'delete', 'global',
+               'gpu_debug_layers')
 
+    device.adb_run_as(package, 'rm', layer_base, quiet=True)
 
-def get_layer():
+
+def get_layer() -> Optional[str]:
     '''
     Find the debug layer to use in the build directory.
+
+    Returns:
+        The part to the library to use.
     '''
 
     base_dir = './build_arm64/source/'
 
-    sym_lib = None
+    # TODO: If we want to use symbolized layer we need to rename it
     lib = None
 
     for path in os.listdir(base_dir):
+        # Match symbolized library first so we don't use it
         if path.endswith('_sym.so'):
-            sym_lib = os.path.join(base_dir, path)
+            _ = os.path.join(base_dir, path)
         elif path.endswith('.so'):
             lib = os.path.join(base_dir, path)
 
-    # TODO: If we want to use symbolized layer we need to rename it
     return lib
 
 
-def parse_command_line():
+def parse_command_line() -> argparse.Namespace:
     '''
     Parse the command line.
 
@@ -200,7 +223,7 @@ def parse_command_line():
     return parser.parse_args()
 
 
-def main():
+def main() -> int:
     '''
     Script main function.
 
@@ -211,6 +234,9 @@ def main():
 
     device = Device()
     layer = get_layer()
+    if not layer:
+        print('ERROR: Layer binary not found')
+        return 1
 
     enable_vulkan_debug_layer(device, args.package, layer)
 
@@ -218,6 +244,9 @@ def main():
 
     disable_vulkan_debug_layer(device, args.package, layer)
 
+    return 0
+
+
 if __name__ == '__main__':
     try:
         sys.exit(main())
diff --git a/layer_gpu_timeline/android_install.py b/layer_gpu_timeline/android_install.py
index dc1e062..e92abf7 100644
--- a/layer_gpu_timeline/android_install.py
+++ b/layer_gpu_timeline/android_install.py
@@ -30,6 +30,7 @@
 import shlex
 import subprocess as sp
 import sys
+from typing import Any, Optional
 
 # Android temp directory
 ANDROID_TMP_DIR = '/data/local/tmp/'
@@ -38,6 +39,7 @@
 EXPECTED_VULKAN_LAYER_NAME = 'VK_LAYER_LGL_GPUTIMELINE'
 EXPECTED_VULKAN_LAYER_FILE = 'libVkLayerGPUTimeline.so'
 
+
 class Device:
     '''
     A basic wrapper around adb, allowing a specific device to be registered.
@@ -46,7 +48,7 @@ class Device:
         device: The name of the device to call, or None for non-specific use.
     '''
 
-    def adb_quiet(self, *args):
+    def adb_quiet(self, *args: str) -> None:
         '''
         Call `adb` to run a command, but ignore output and errors.
 
@@ -57,7 +59,7 @@ def adb_quiet(self, *args):
         commands.extend(args)
         sp.run(commands, stdout=sp.DEVNULL, stderr=sp.DEVNULL, check=False)
 
-    def adb(self, *args, **kwargs):
+    def adb(self, *args: str, **kwargs: Any) -> str:
         '''
         Call `adb` to run command, and capture output and results.
 
@@ -73,7 +75,7 @@ def adb(self, *args, **kwargs):
         Raises:
             CalledProcessError: The subprocess was not successfully executed.
         '''
-        commands = ['adb']
+        commands = ['adb']  # type: Any
         commands.extend(args)
 
         text = kwargs.get('text', True)
@@ -84,12 +86,12 @@ def adb(self, *args, **kwargs):
         if shell:
             # Unix shells need a flattened command for shell commands
             if os.name != 'nt':
-                quotedCommands = []
+                quoted_commands = []
                 for command in commands:
                     if command != '>':
                         command = shlex.quote(command)
-                    quotedCommands.append(command)
-                commands = ' '.join(quotedCommands)
+                    quoted_commands.append(command)
+                commands = ' '.join(quoted_commands)
 
         # Run on the device but with shell argument quoting
         if quote:
@@ -101,11 +103,13 @@ def adb(self, *args, **kwargs):
 
         return rep.stdout
 
-    def adb_run_as(self, package, *args, quiet=False):
+    def adb_run_as(self, package: str,
+                   *args: str, quiet: bool = False) -> Optional[str]:
         '''
         Call `adb` to run command as a package using `run-as` or as root,
         if root is accessible. If command will be run as root, this function
-        will change CWD to the package data directory before executing the command.
+        will change CWD to the package data directory before executing the
+        command.
 
         Args:
             package: Package name to run-as or change CWD to.
@@ -113,7 +117,7 @@ def adb_run_as(self, package, *args, quiet=False):
             quiet: If True, ignores output from adb.
 
         Returns:
-            The contents of stdout or Nothing, if quiet=True.
+            The contents of stdout or None if quiet=True.
 
         Raises:
             CalledProcessError: The subprocess was not successfully executed.
@@ -122,12 +126,14 @@ def adb_run_as(self, package, *args, quiet=False):
         command.extend(args)
 
         if quiet:
-            return self.adb_quiet(*command)
+            self.adb_quiet(*command)
+            return None
 
         return self.adb(*command)
 
 
-def enable_vulkan_debug_layer(device, package, layer):
+def enable_vulkan_debug_layer(
+        device: Device, package: str, layer: str) -> None:
     '''
     Args:
         device: The device instance.
@@ -138,16 +144,24 @@ def enable_vulkan_debug_layer(device, package, layer):
     print('\nInstalling Vulkan debug layer')
 
     layer = os.path.normpath(layer)
-    layerBase = os.path.basename(os.path.normpath(layer))
+    layer_base = os.path.basename(os.path.normpath(layer))
 
     device.adb('push', layer, ANDROID_TMP_DIR)
-    device.adb_run_as(package, 'cp', ANDROID_TMP_DIR + layerBase, '.')
-    device.adb('shell', 'settings', 'put', 'global', 'enable_gpu_debug_layers', '1')
-    device.adb('shell', 'settings', 'put', 'global', 'gpu_debug_app', package)
-    device.adb('shell', 'settings', 'put', 'global', 'gpu_debug_layers', EXPECTED_VULKAN_LAYER_NAME)
 
+    device.adb_run_as(package, 'cp', ANDROID_TMP_DIR + layer_base, '.')
+
+    device.adb('shell', 'settings', 'put', 'global',
+               'enable_gpu_debug_layers', '1')
+
+    device.adb('shell', 'settings', 'put', 'global',
+               'gpu_debug_app', package)
 
-def disable_vulkan_debug_layer(device, package, layer):
+    device.adb('shell', 'settings', 'put', 'global',
+               'gpu_debug_layers', EXPECTED_VULKAN_LAYER_NAME)
+
+
+def disable_vulkan_debug_layer(
+        device: Device, package: str, layer: str) -> None:
     '''
     Clean up the Vulkan layer installation.
 
@@ -157,35 +171,44 @@ def disable_vulkan_debug_layer(device, package, layer):
     '''
     print('\nRemoving Vulkan debug layer')
 
-    layerBase = os.path.basename(os.path.normpath(layer))
+    layer_base = os.path.basename(os.path.normpath(layer))
+
+    device.adb('shell', 'settings', 'delete', 'global',
+               'enable_gpu_debug_layers')
+
+    device.adb('shell', 'settings', 'delete', 'global',
+               'gpu_debug_app')
 
-    device.adb('shell', 'settings', 'delete', 'global', 'enable_gpu_debug_layers')
-    device.adb('shell', 'settings', 'delete', 'global gpu_debug_app')
-    device.adb('shell', 'settings', 'delete', 'global gpu_debug_layers')
-    device.adb_run_as(package, 'rm', layerBase, quiet=True)
+    device.adb('shell', 'settings', 'delete', 'global',
+               'gpu_debug_layers')
 
+    device.adb_run_as(package, 'rm', layer_base, quiet=True)
 
-def get_layer():
+
+def get_layer() -> Optional[str]:
     '''
     Find the debug layer to use in the build directory.
+
+    Returns:
+        The part to the library to use.
     '''
 
     base_dir = './build_arm64/source/'
 
-    sym_lib = None
+    # TODO: If we want to use symbolized layer we need to rename it
     lib = None
 
     for path in os.listdir(base_dir):
+        # Match symbolized library first so we don't use it
         if path.endswith('_sym.so'):
-            sym_lib = os.path.join(base_dir, path)
+            _ = os.path.join(base_dir, path)
         elif path.endswith('.so'):
             lib = os.path.join(base_dir, path)
 
-    # TODO: If we want to use symbolized layer we need to rename it
     return lib
 
 
-def parse_command_line():
+def parse_command_line() -> argparse.Namespace:
     '''
     Parse the command line.
 
@@ -200,7 +223,7 @@ def parse_command_line():
     return parser.parse_args()
 
 
-def main():
+def main() -> int:
     '''
     Script main function.
 
@@ -211,6 +234,9 @@ def main():
 
     device = Device()
     layer = get_layer()
+    if not layer:
+        print('ERROR: Layer binary not found')
+        return 1
 
     enable_vulkan_debug_layer(device, args.package, layer)
 
@@ -218,6 +244,9 @@ def main():
 
     disable_vulkan_debug_layer(device, args.package, layer)
 
+    return 0
+
+
 if __name__ == '__main__':
     try:
         sys.exit(main())