Fetch MCP Server

Instructions

Implementation Reference

• src/Fetcher.ts:127-148 (handler)

  The core handler function for fetch_markdown tool. Fetches the URL, converts HTML to Markdown using TurndownService, applies length limits, and returns the content.

  static async markdown(requestPayload: RequestPayload) {
    try {
      const response = await this._fetch(requestPayload);
      const html = await response.text();
      const turndownService = new TurndownService();
      let markdown = turndownService.turndown(html);
      
      // Apply length limits
      markdown = this.applyLengthLimits(
        markdown,
        requestPayload.max_length ?? 5000,
        requestPayload.start_index ?? 0
      );
      
      return { content: [{ type: "text", text: markdown }], isError: false };
    } catch (error) {
      return {
        content: [{ type: "text", text: (error as Error).message }],
        isError: true,
      };
    }
  }

• src/index.ts:56-81 (schema)

  Tool schema definition including input schema for fetch_markdown, registered in ListTools response.

  {
    name: "fetch_markdown",
    description: "Fetch a website and return its contents converted content to 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",
        },
        max_length: {
          type: "number",
          description: `Maximum number of characters to return (default: ${downloadLimit}})`,
        },
        start_index: {
          type: "number",
          description: "Start content from this character index (default: 0)",
        },
      },
      required: ["url"],
    },
  },

• src/index.ts:156-159 (registration)

  Registration of the fetch_markdown handler in the CallToolRequestSchema handler, dispatching to Fetcher.markdown.

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

• src/types.ts:5-10 (schema)

  Shared Zod schema for request payload validation, used for all fetch tools including fetch_markdown.

  export const RequestPayloadSchema = z.object({
    url: z.string().url(),
    headers: z.record(z.string()).optional(),
    max_length: z.number().int().min(0).optional().default(downloadLimit),
    start_index: z.number().int().min(0).optional().default(0),
  });

• src/Fetcher.ts:7-14 (helper)

  Helper method to apply max_length and start_index limits to the fetched content.

  private static applyLengthLimits(text: string, maxLength: number, startIndex: number): string {
    if (startIndex >= text.length) {
      return "";
    }
    
    const end = maxLength > 0 ? Math.min(startIndex + maxLength, text.length) : text.length;
    return text.substring(startIndex, end);
  }