feat: improve TypeScript type safety and add structured logging

README.md

@@ -33,6 +33,7 @@ Advanced reasoning and problem-solving using the `sonar-reasoning-pro` model. Pe
 1. Get your Perplexity API Key from the [API Portal](https://www.perplexity.ai/account/api/group)
 2. Set it as an environment variable: `PERPLEXITY_API_KEY=your_key_here`
 3. (Optional) Set a timeout for requests: `PERPLEXITY_TIMEOUT_MS=600000`. The default is 5 minutes.
+4. (Optional) Set log level for debugging: `PERPLEXITY_LOG_LEVEL=DEBUG|INFO|WARN|ERROR`. The default is ERROR.
 
 ### Claude Code
 

src/http.ts

@@ -4,11 +4,12 @@ import express from "express";
 import cors from "cors";
 import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
 import { createPerplexityServer } from "./server.js";
+import { logger } from "./logger.js";
 
 // Check for required API key
 const PERPLEXITY_API_KEY = process.env.PERPLEXITY_API_KEY;
 if (!PERPLEXITY_API_KEY) {
-  console.error("Error: PERPLEXITY_API_KEY environment variable is required");
+  logger.error("PERPLEXITY_API_KEY environment variable is required");
   process.exit(1);
 }
 
@@ -62,7 +63,7 @@ app.all("/mcp", async (req, res) => {
 
     await transport.handleRequest(req, res, req.body);
   } catch (error) {
-    console.error("Error handling MCP request:", error);
+    logger.error("Error handling MCP request", { error: String(error) });
     if (!res.headersSent) {
       res.status(500).json({
         jsonrpc: "2.0",
@@ -84,10 +85,10 @@ app.get("/health", (req, res) => {
  * Start the HTTP server
  */
 app.listen(PORT, BIND_ADDRESS, () => {
-  console.log(`Perplexity MCP Server listening on http://${BIND_ADDRESS}:${PORT}/mcp`);
-  console.log(`Allowed origins: ${ALLOWED_ORIGINS.join(", ")}`);
+  logger.info(`Perplexity MCP Server listening on http://${BIND_ADDRESS}:${PORT}/mcp`);
+  logger.info(`Allowed origins: ${ALLOWED_ORIGINS.join(", ")}`);
 }).on("error", (error) => {
-  console.error("Server error:", error);
+  logger.error("Server error", { error: String(error) });
   process.exit(1);
 });
 

src/index.test.ts

@@ -48,7 +48,7 @@ describe("Perplexity MCP Server", () => {
     });
 
     it("should handle missing results array", () => {
-      const mockData = {};
+      const mockData = {} as any;
       const formatted = formatSearchResults(mockData);
       expect(formatted).toBe("No search results found.");
     });
@@ -260,7 +260,7 @@ describe("Perplexity MCP Server", () => {
       const messages = [{ role: "user", content: "test" }];
 
       await expect(performChatCompletion(messages)).rejects.toThrow(
-        "missing or empty choices array"
+        "Invalid API response"
       );
     });
 
@@ -273,7 +273,7 @@ describe("Perplexity MCP Server", () => {
       const messages = [{ role: "user", content: "test" }];
 
       await expect(performChatCompletion(messages)).rejects.toThrow(
-        "missing message content"
+        "Invalid API response"
       );
     });
 
@@ -286,7 +286,7 @@ describe("Perplexity MCP Server", () => {
       const messages = [{ role: "user", content: "test" }];
 
       await expect(performChatCompletion(messages)).rejects.toThrow(
-        "missing or empty choices array"
+        "Invalid API response"
       );
     });
 
@@ -299,7 +299,7 @@ describe("Perplexity MCP Server", () => {
       const messages = [{ role: "user", content: "test" }];
 
       await expect(performChatCompletion(messages)).rejects.toThrow(
-        "missing message content"
+        "Invalid API response"
       );
     });
 
@@ -312,7 +312,7 @@ describe("Perplexity MCP Server", () => {
       const messages = [{ role: "user", content: "test" }];
 
       await expect(performChatCompletion(messages)).rejects.toThrow(
-        "missing or empty choices array"
+        "Invalid API response"
       );
     });
 
@@ -325,7 +325,7 @@ describe("Perplexity MCP Server", () => {
       const messages = [{ role: "user", content: "test" }];
 
       await expect(performChatCompletion(messages)).rejects.toThrow(
-        "missing message content"
+        "Invalid API response"
       );
     });
 
@@ -359,10 +359,10 @@ describe("Perplexity MCP Server", () => {
       } as Response);
 
       const messages = [{ role: "user", content: "test" }];
-      const result = await performChatCompletion(messages);
 
-      expect(result).toBe("Response");
-      expect(result).not.toContain("Citations:");
+      await expect(performChatCompletion(messages)).rejects.toThrow(
+        "Invalid API response"
+      );
     });
   });
 
@@ -378,7 +378,7 @@ describe("Perplexity MCP Server", () => {
       const messages = [{ role: "user", content: "test" }];
 
       await expect(performChatCompletion(messages)).rejects.toThrow(
-        "Failed to parse JSON response"
+        "Invalid API response"
       );
     });
 
@@ -588,7 +588,7 @@ describe("Perplexity MCP Server", () => {
           { title: null, url: "https://example.com", snippet: undefined },
           { title: "Valid", url: null, snippet: "snippet", date: undefined },
         ],
-      };
+      } as any;
 
       const formatted = formatSearchResults(mockData);
 

src/logger.ts

@@ -0,0 +1,93 @@
+/**
+ * Simple structured logger for the Perplexity MCP Server
+ * Outputs to stderr to avoid interfering with STDIO transport
+ */
+
+export enum LogLevel {
+  DEBUG = 0,
+  INFO = 1,
+  WARN = 2,
+  ERROR = 3,
+}
+
+const LOG_LEVEL_NAMES: Record<LogLevel, string> = {
+  [LogLevel.DEBUG]: "DEBUG",
+  [LogLevel.INFO]: "INFO",
+  [LogLevel.WARN]: "WARN",
+  [LogLevel.ERROR]: "ERROR",
+};
+
+/**
+ * Gets the configured log level from environment variable
+ * Defaults to ERROR to minimize noise in production
+ */
+function getLogLevel(): LogLevel {
+  const level = process.env.PERPLEXITY_LOG_LEVEL?.toUpperCase();
+  switch (level) {
+    case "DEBUG":
+      return LogLevel.DEBUG;
+    case "INFO":
+      return LogLevel.INFO;
+    case "WARN":
+      return LogLevel.WARN;
+    case "ERROR":
+      return LogLevel.ERROR;
+    default:
+      return LogLevel.ERROR;
+  }
+}
+
+const currentLogLevel = getLogLevel();
+
+function safeStringify(obj: unknown): string {
+  try {
+    return JSON.stringify(obj);
+  } catch {
+    return "[Unstringifiable]";
+  }
+}
+
+/**
+ * Formats a log message with timestamp and level
+ */
+function formatMessage(level: LogLevel, message: string, meta?: Record<string, unknown>): string {
+  const timestamp = new Date().toISOString();
+  const levelName = LOG_LEVEL_NAMES[level];
+
+  if (meta && Object.keys(meta).length > 0) {
+    return `[${timestamp}] ${levelName}: ${message} ${safeStringify(meta)}`;
+  }
+
+  return `[${timestamp}] ${levelName}: ${message}`;
+}
+
+/**
+ * Logs a message if the configured log level allows it
+ */
+function log(level: LogLevel, message: string, meta?: Record<string, unknown>): void {
+  if (level >= currentLogLevel) {
+    const formatted = formatMessage(level, message, meta);
+    console.error(formatted); // Use stderr to avoid interfering with STDIO
+  }
+}
+
+/**
+ * Structured logger interface
+ */
+export const logger = {
+  debug(message: string, meta?: Record<string, unknown>): void {
+    log(LogLevel.DEBUG, message, meta);
+  },
+
+  info(message: string, meta?: Record<string, unknown>): void {
+    log(LogLevel.INFO, message, meta);
+  },
+
+  warn(message: string, meta?: Record<string, unknown>): void {
+    log(LogLevel.WARN, message, meta);
+  },
+
+  error(message: string, meta?: Record<string, unknown>): void {
+    log(LogLevel.ERROR, message, meta);
+  },
+};