MCP Node Fetch

Instructions

Implementation Reference

• src/index.ts:381-431 (handler)

  The handler function that executes the check-status tool logic: sends a HEAD request to the URL and returns status information, headers, and availability.

  async function handleCheckStatus(args: CheckStatusArgs): Promise<z.infer<typeof CallToolResultSchema>> {
    try {
      const { url, timeout } = args;
      
      console.error(`Checking status of ${url}`);
      
      // Create request options
      const options: any = {
        method: "HEAD",
      };
      
      if (timeout) {
        // @ts-ignore - undici specific options
        options.headersTimeout = timeout;
      }
      
      // Perform the request
      const response = await fetch(url, options);
      
      // Create a result object
      const result = {
        status: response.status,
        statusText: response.statusText,
        headers: Object.fromEntries(response.headers.entries()),
        url: response.url,
        isAvailable: response.ok,
      };
      
      return {
        content: [
          {
            type: "text",
            text: JSON.stringify(result, null, 2)
          }
        ]
      };
    } catch (error) {
      console.error(`Error checking URL status:`, error);
      return {
        isError: true,
        content: [
          {
            type: "text",
            text: `Error checking URL status: ${(error as Error).message}`
          }
        ]
      };
    }
  }
  
  // Start the server using stdio transport

• src/index.ts:38-41 (schema)

  Zod schema used for input validation in the check-status handler.

  const CheckStatusArgsSchema = z.object({
    url: z.string().url().describe("URL to check"),
    timeout: z.number().positive().optional().describe("Request timeout in milliseconds")
  });

• src/index.ts:120-131 (registration)

  Tool registration in the TOOLS array, defining name, description, and JSON input schema.

  {
    name: "check-status",
    description: "Check if a URL is accessible (HEAD request)",
    inputSchema: {
      type: "object",
      properties: {
        url: { type: "string", description: "URL to check" },
        timeout: { type: "number", description: "Request timeout in milliseconds" }
      },
      required: ["url"]
    }
  }

• src/index.ts:46-46 (schema)

  TypeScript type definition for check-status arguments inferred from the Zod schema.

  type CheckStatusArgs = z.infer<typeof CheckStatusArgsSchema>;

• src/index.ts:163-164 (registration)

  Dispatch case in the CallToolRequestSchema handler that routes to the check-status handler.

  case "check-status":
    return handleCheckStatus(CheckStatusArgsSchema.parse(args));