Fetch MCP Server

Instructions

Implementation Reference

• src/Fetcher.ts:90-103 (handler)

  The primary handler function executing the fetch_markdown tool: fetches HTML from the URL and converts it to Markdown using TurndownService.

  static async markdown(requestPayload: RequestPayload) {
    try {
      const response = await this._fetch(requestPayload);
      const html = await response.text();
      const turndownService = new TurndownService();
      const markdown = turndownService.turndown(html);
      return { content: [{ type: "text", text: markdown }], isError: false };
    } catch (error) {
      return {
        content: [{ type: "text", text: (error as Error).message }],
        isError: true,
      };
    }
  }

• src/types.ts:3-6 (schema)

  Zod schema defining the input structure for fetch_markdown (and other fetch tools): requires a valid URL and optional headers.

  export const RequestPayloadSchema = z.object({
    url: z.string().url(),
    headers: z.record(z.string()).optional(),
  });

• src/index.ts:46-63 (registration)

  Tool registration in the ListTools response, providing name, description, and input schema.

  {
    name: "fetch_markdown",
    description: "Fetch a website and return the content as Markdown",
    inputSchema: {
      type: "object",
      properties: {
        url: {
          type: "string",
          description: "URL of the website to fetch",
        },
        headers: {
          type: "object",
          description: "Optional headers to include in the request",
        },
      },
      required: ["url"],
    },
  },

• src/index.ts:122-125 (handler)

  Dispatch logic in the CallToolRequestHandler that routes fetch_markdown calls to the Fetcher.markdown implementation.

  if (request.params.name === "fetch_markdown") {
    const fetchResult = await Fetcher.markdown(validatedArgs);
    return fetchResult;
  }

• src/Fetcher.ts:6-30 (helper)

  Shared private helper method for performing the HTTP fetch request with custom User-Agent and error handling, used by markdown handler.

  private static async _fetch({
    url,
    headers,
  }: RequestPayload): Promise<Response> {
    try {
      const response = await fetch(url, {
        headers: {
          "User-Agent":
            "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36",
          ...headers,
        },
      });
  
      if (!response.ok) {
        throw new Error(`HTTP error: ${response.status}`);
      }
      return response;
    } catch (e: unknown) {
      if (e instanceof Error) {
        throw new Error(`Failed to fetch ${url}: ${e.message}`);
      } else {
        throw new Error(`Failed to fetch ${url}: Unknown error`);
      }
    }
  }