GraphQL MCP Server

Instructions

Implementation Reference

• src/index.ts:78-113 (registration)

  Registration of the "introspect" MCP tool using server.tool(), including input schema and inline handler function.
  server.tool( "introspect", "Introspect the GraphQL schema, use this tool before doing a query to get the schema information if you do not have it available as a resource already.", { // This is a workaround to help clients that can't handle an empty object as an argument // They will often send undefined instead of an empty object which is not allowed by the schema __ignore__: z .boolean() .default(false) .describe("This does not do anything"), }, async () => { try { const schema = await introspectEndpoint(env.ENDPOINT, env.HEADERS); return { content: [ { type: "text", text: schema, }, ], }; } catch (error) { return { isError: true, content: [ { type: "text", text: `Failed to introspect schema: ${error}`, }, ], }; } } );
• src/index.ts:89-112 (handler)

  Inline handler function for the "introspect" tool that calls introspectEndpoint and returns the GraphQL schema as text content or error.
  async () => { try { const schema = await introspectEndpoint(env.ENDPOINT, env.HEADERS); return { content: [ { type: "text", text: schema, }, ], }; } catch (error) { return { isError: true, content: [ { type: "text", text: `Failed to introspect schema: ${error}`, }, ], }; } }
• src/index.ts:81-88 (schema)

  Input schema for the "introspect" tool using Zod (dummy __ignore__ boolean field to workaround client issues with empty objects).
  { // This is a workaround to help clients that can't handle an empty object as an argument // They will often send undefined instead of an empty object which is not allowed by the schema __ignore__: z .boolean() .default(false) .describe("This does not do anything"), },
• src/helpers/introspection.ts:8-33 (helper)

  Helper function 'introspectEndpoint' that performs GraphQL introspection query on the endpoint and returns the schema in SDL format.
  export async function introspectEndpoint( endpoint: string, headers?: Record<string, string>, ) { const response = await fetch(endpoint, { method: "POST", headers: { "Content-Type": "application/json", ...headers, }, body: JSON.stringify({ query: getIntrospectionQuery(), }), }); if (!response.ok) { throw new Error(`GraphQL request failed: ${response.statusText}`); } const responseJson = (await response.json()) as any; // Transform to a schema object const schema = buildClientSchema(responseJson.data); // Print the schema SDL return printSchema(schema); }