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fix(core): relax tool name validation to support unprefixed MCP tools #15522

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fix(core): relax tool name validation to support unprefixed MCP tools #15522

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60e959f
feat: allow any valid slug for tool names, removing server and tool p…
kevin-ramdass Dec 24, 2025
102b371
feat: validate generic slug names as valid tool names
kevin-ramdass Dec 24, 2025
ca81bdb
test: update agent TOML tools test case
kevin-ramdass Dec 24, 2025
f99d878
Merge branch 'main' into kevin-ramdass/agents
kevin-ramdass Dec 26, 2025
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2 changes: 1 addition & 1 deletion packages/core/src/agents/toml-loader.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -107,7 +107,7 @@ describe('toml-loader', () => {
const filePath = await writeAgentToml(`
name = "test-agent"
description = "A test agent"
tools = ["not-a-tool"]
tools = ["tool!"]
[prompts]
system_prompt = "You are a test agent."
`);
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7 changes: 6 additions & 1 deletion packages/core/src/tools/tool-names.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,14 @@ describe('tool-names', () => {
expect(isValidToolName('my-server__my-tool')).toBe(true);
});

it('should validate generic slug names (unprefixed tools)', () => {
expect(isValidToolName('search_for_files_codesearch')).toBe(true);
expect(isValidToolName('simple-tool-name')).toBe(true);
expect(isValidToolName('tool_with_underscores')).toBe(true);
});

it('should reject invalid tool names', () => {
expect(isValidToolName('')).toBe(false);
expect(isValidToolName('invalid-name')).toBe(false);
expect(isValidToolName('server__')).toBe(false);
expect(isValidToolName('__tool')).toBe(false);
expect(isValidToolName('server__tool__extra')).toBe(false);
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4 changes: 3 additions & 1 deletion packages/core/src/tools/tool-names.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -88,5 +88,7 @@ export function isValidToolName(
return slugRegex.test(server) && slugRegex.test(tool);
}

return false;
// Allow any valid slug to support unprefixed MCP tools or other dynamic tools
const slugRegex = /^[a-z0-9-_]+$/i;
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@gemini-code-assist gemini-code-assist bot Dec 24, 2025

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high

The current regex allows tool names like constructor and prototype. If these tool names are later used as keys in plain JavaScript objects, this could lead to prototype pollution vulnerabilities. It's safer to explicitly disallow these names in the regex.

Note that the same vulnerability exists for the namespaced tool validation on line 87. While that line is not part of this diff, it should also be updated to prevent this vulnerability for namespaced tools (e.g., server__constructor).

Suggested change
const slugRegex = /^[a-z0-9-_]+$/i;
const slugRegex = /^(?!(?:constructor|prototype)$)[a-z0-9-_]+$/i;

return slugRegex.test(name);
}