lookup

Instructions

Implementation Reference

• src/tools/lookup.ts:25-35 (handler)

  The asynchronous handler function for the 'lookup' tool. It takes a query, performs a chat completion using Perplexity's 'sonar-pro' model with the LOOKUP_SYSTEM_PROMPT, and returns the result as text content.

  async ({ query }) => {
    const result = await performChatCompletion(
      [{ role: "user", content: query }],
      {
        model: "sonar-pro",
        system: LOOKUP_SYSTEM_PROMPT,
        searchContextSize: "medium",
      },
    );
    return { content: [{ type: "text", text: result }] };
  },

• src/tools/lookup.ts:13-24 (schema)

  The schema definition for the 'lookup' tool, including description and inputSchema using Zod for the 'query' parameter.

      {
        description: `
  Fetches precise, source-backed facts from official sources.
  Use for API syntax/params, config keys/defaults, CLI flags, runtime compatibility, and package metadata (types, ESM/CJS, side-effects).
  Returns short, factual answers. No recommendations or comparisons.
  Examples: "What's the default timeout for fetch()?", "What parameters does useState accept?", "Show me how Zod validates email addresses"
  One question per call—split combined requests into separate queries.
  `.trim(),
        inputSchema: {
          query: z.string().describe("The documentation query to look up"),
        },
      },

• src/tools/lookup.ts:10-37 (registration)

  The registerLookupTool function that registers the 'lookup' tool with the MCP server, including its schema and handler.

  export function registerLookupTool(server: McpServer) {
    server.registerTool(
      "lookup",
      {
        description: `
  Fetches precise, source-backed facts from official sources.
  Use for API syntax/params, config keys/defaults, CLI flags, runtime compatibility, and package metadata (types, ESM/CJS, side-effects).
  Returns short, factual answers. No recommendations or comparisons.
  Examples: "What's the default timeout for fetch()?", "What parameters does useState accept?", "Show me how Zod validates email addresses"
  One question per call—split combined requests into separate queries.
  `.trim(),
        inputSchema: {
          query: z.string().describe("The documentation query to look up"),
        },
      },
      async ({ query }) => {
        const result = await performChatCompletion(
          [{ role: "user", content: query }],
          {
            model: "sonar-pro",
            system: LOOKUP_SYSTEM_PROMPT,
            searchContextSize: "medium",
          },
        );
        return { content: [{ type: "text", text: result }] };
      },
    );
  }

• src/server.ts:17-17 (registration)

  The call to register the 'lookup' tool during server setup.

  registerLookupTool(server);

• src/prompts.ts:45-68 (helper)

  The system prompt used by the 'lookup' tool handler for guiding fact extraction from sources.

  export const LOOKUP_SYSTEM_PROMPT = `
  # Role: Fact Extraction Agent
  Extract precise, verifiable facts from source code and documentation. Optimized for quick lookups of:
  - API signatures and parameter types
  - Configuration keys and default values
  - CLI flags and options
  - Package metadata (versions, exports, compatibility)
  - Exact error messages and codes
  
  # Instructions
  - Search GitHub source code FIRST - find the exact line where something is defined/used
  - Return the specific fact requested, nothing more
  - Include file path and line numbers when citing code
  - State "Not found in available sources" if information doesn't exist
  - Avoid explanations unless the fact itself is ambiguous
  
  ${AUTHORITATIVE_SOURCES}
  
  # Output Format
  - Direct answer with source citation: "The default value is X [repo/file.ts:123]"
  - For code usage: Show the exact line(s) from source
  - For missing info: "Not found in available sources"
  - No preamble, no "Based on my search...", just the fact
  `.trim();