Filesystem MCP Server

Instructions

Input Schema

Input Schema (JSON Schema)

Implementation Reference

• src/filesystem/index.ts:248-278 (handler)

  The core handler function for the 'read_media_file' tool. It validates the file path, determines the MIME type based on the file extension, reads the file content as a Base64-encoded string using a helper function, determines the content type (image, audio, or blob), and returns the appropriately structured content for MCP.
  async (args: z.infer<typeof ReadMediaFileArgsSchema>) => { const validPath = await validatePath(args.path); const extension = path.extname(validPath).toLowerCase(); const mimeTypes: Record<string, string> = { ".png": "image/png", ".jpg": "image/jpeg", ".jpeg": "image/jpeg", ".gif": "image/gif", ".webp": "image/webp", ".bmp": "image/bmp", ".svg": "image/svg+xml", ".mp3": "audio/mpeg", ".wav": "audio/wav", ".ogg": "audio/ogg", ".flac": "audio/flac", }; const mimeType = mimeTypes[extension] || "application/octet-stream"; const data = await readFileAsBase64Stream(validPath); const type = mimeType.startsWith("image/") ? "image" : mimeType.startsWith("audio/") ? "audio" // Fallback for other binary types, not officially supported by the spec but has been used for some time : "blob"; const contentItem = { type: type as 'image' | 'audio' | 'blob', data, mimeType }; return { content: [contentItem], structuredContent: { content: [contentItem] } } as unknown as CallToolResult; }
• src/filesystem/index.ts:83-85 (schema)

  Zod schema defining the input arguments for the 'read_media_file' tool (path: string). Used for typing the handler function arguments.
  const ReadMediaFileArgsSchema = z.object({ path: z.string() });
• src/filesystem/index.ts:229-279 (registration)

  Registration of the 'read_media_file' tool with the MCP server, including title, description, input/output schemas, annotations, and reference to the inline handler function.
  server.registerTool( "read_media_file", { title: "Read Media File", description: "Read an image or audio file. Returns the base64 encoded data and MIME type. " + "Only works within allowed directories.", inputSchema: { path: z.string() }, outputSchema: { content: z.array(z.object({ type: z.enum(["image", "audio", "blob"]), data: z.string(), mimeType: z.string() })) }, annotations: { readOnlyHint: true } }, async (args: z.infer<typeof ReadMediaFileArgsSchema>) => { const validPath = await validatePath(args.path); const extension = path.extname(validPath).toLowerCase(); const mimeTypes: Record<string, string> = { ".png": "image/png", ".jpg": "image/jpeg", ".jpeg": "image/jpeg", ".gif": "image/gif", ".webp": "image/webp", ".bmp": "image/bmp", ".svg": "image/svg+xml", ".mp3": "audio/mpeg", ".wav": "audio/wav", ".ogg": "audio/ogg", ".flac": "audio/flac", }; const mimeType = mimeTypes[extension] || "application/octet-stream"; const data = await readFileAsBase64Stream(validPath); const type = mimeType.startsWith("image/") ? "image" : mimeType.startsWith("audio/") ? "audio" // Fallback for other binary types, not officially supported by the spec but has been used for some time : "blob"; const contentItem = { type: type as 'image' | 'audio' | 'blob', data, mimeType }; return { content: [contentItem], structuredContent: { content: [contentItem] } } as unknown as CallToolResult; } );
• src/filesystem/index.ts:154-167 (helper)

  Helper utility function to read a file as a stream of buffers, concatenate them, and encode to Base64 string. Memory-efficient for handling binary media files. Called by the read_media_file handler.
  async function readFileAsBase64Stream(filePath: string): Promise<string> { return new Promise((resolve, reject) => { const stream = createReadStream(filePath); const chunks: Buffer[] = []; stream.on('data', (chunk) => { chunks.push(chunk as Buffer); }); stream.on('end', () => { const finalBuffer = Buffer.concat(chunks); resolve(finalBuffer.toString('base64')); }); stream.on('error', (err) => reject(err)); }); }