Advanced Hasura GraphQL MCP Server

Instructions

Implementation Reference

• src/index.ts:444-464 (handler)

  The asynchronous handler function that executes the health_check tool. It checks the Hasura GraphQL endpoint reachability using a simple GraphQL query or an optional HTTP health endpoint via fetch.

  async ({ healthEndpointUrl }) => {
    console.log(`[INFO] Executing tool 'health_check'...`);
    try {
        let resultText = "";
        if (healthEndpointUrl) {
            console.log(`[DEBUG] Performing HTTP GET to: ${healthEndpointUrl}`);
            const response = await fetch(healthEndpointUrl, { method: 'GET' });
            resultText = `Health endpoint ${healthEndpointUrl} status: ${response.status} ${response.statusText}`;
             if (!response.ok) throw new Error(resultText);
        } else {
            console.log(`[DEBUG] Performing GraphQL query { __typename } to: ${HASURA_ENDPOINT}`);
            const query = gql`query HealthCheck { __typename }`;
            const result = await makeGqlRequest(query);
            resultText = `GraphQL endpoint ${HASURA_ENDPOINT} is responsive. Result: ${JSON.stringify(result)}`;
        }
         return { content: [{ type: "text", text: `Health check successful. ${resultText}` }] };
    } catch (error: any) {
        console.error(`[ERROR] Tool 'health_check' failed: ${error.message}`);
         return { content: [{ type: "text", text: `Health check failed: ${error.message}` }], isError: false }; 
    }
  }

• src/index.ts:441-443 (schema)

  Zod schema defining the input parameters for the health_check tool: an optional URL for a specific health endpoint.

  {
    healthEndpointUrl: z.string().url().optional().describe("Optional. A specific HTTP health check URL...")
  },

• src/index.ts:438-465 (registration)

  The server.tool() call that registers the 'health_check' tool, including its name, description, input schema, and handler function.

  server.tool(
    "health_check",
    "Checks if the configured Hasura GraphQL endpoint is reachable...",
    {
      healthEndpointUrl: z.string().url().optional().describe("Optional. A specific HTTP health check URL...")
    },
    async ({ healthEndpointUrl }) => {
      console.log(`[INFO] Executing tool 'health_check'...`);
      try {
          let resultText = "";
          if (healthEndpointUrl) {
              console.log(`[DEBUG] Performing HTTP GET to: ${healthEndpointUrl}`);
              const response = await fetch(healthEndpointUrl, { method: 'GET' });
              resultText = `Health endpoint ${healthEndpointUrl} status: ${response.status} ${response.statusText}`;
               if (!response.ok) throw new Error(resultText);
          } else {
              console.log(`[DEBUG] Performing GraphQL query { __typename } to: ${HASURA_ENDPOINT}`);
              const query = gql`query HealthCheck { __typename }`;
              const result = await makeGqlRequest(query);
              resultText = `GraphQL endpoint ${HASURA_ENDPOINT} is responsive. Result: ${JSON.stringify(result)}`;
          }
           return { content: [{ type: "text", text: `Health check successful. ${resultText}` }] };
      } catch (error: any) {
          console.error(`[ERROR] Tool 'health_check' failed: ${error.message}`);
           return { content: [{ type: "text", text: `Health check failed: ${error.message}` }], isError: false }; 
      }
    }
  );