Filesystem MCP Server

Instructions

Implementation Reference

• src/filesystem/index.ts:416-426 (handler)

  The handler function that validates the path, reads directory entries using fs.readdir, formats them with [DIR]/[FILE] prefixes, and returns the formatted list.

  async (args: z.infer<typeof ListDirectoryArgsSchema>) => {
    const validPath = await validatePath(args.path);
    const entries = await fs.readdir(validPath, { withFileTypes: true });
    const formatted = entries
      .map((entry) => `${entry.isDirectory() ? "[DIR]" : "[FILE]"} ${entry.name}`)
      .join("\n");
    return {
      content: [{ type: "text" as const, text: formatted }],
      structuredContent: { content: formatted }
    };
  }

• src/filesystem/index.ts:401-427 (registration)

  Tool registration using server.registerTool, specifying the name 'list_directory', title, description, input/output schemas, annotations, and the handler function.

  server.registerTool(
    "list_directory",
    {
      title: "List Directory",
      description:
        "Get a detailed listing of all files and directories in a specified path. " +
        "Results clearly distinguish between files and directories with [FILE] and [DIR] " +
        "prefixes. This tool is essential for understanding directory structure and " +
        "finding specific files within a directory. Only works within allowed directories.",
      inputSchema: {
        path: z.string()
      },
      outputSchema: { content: z.string() },
      annotations: { readOnlyHint: true }
    },
    async (args: z.infer<typeof ListDirectoryArgsSchema>) => {
      const validPath = await validatePath(args.path);
      const entries = await fs.readdir(validPath, { withFileTypes: true });
      const formatted = entries
        .map((entry) => `${entry.isDirectory() ? "[DIR]" : "[FILE]"} ${entry.name}`)
        .join("\n");
      return {
        content: [{ type: "text" as const, text: formatted }],
        structuredContent: { content: formatted }
      };
    }
  );

• src/filesystem/index.ts:114-116 (schema)

  Zod schema for input arguments of the list_directory tool, defining the required 'path' parameter.

  const ListDirectoryArgsSchema = z.object({
    path: z.string(),
  });