exif-mcp

Instructions

Implementation Reference

• src/tools/index.ts:205-219 (handler)

  The main handler function that loads the image buffer using loadImage and retrieves rotation/flip info using exifr.rotation.

  async (args, extra) => {
    try {
      const { image } = args;
      const buf = await loadImage(image);
      const rotation = await exifr.rotation(buf);
      
      if (!rotation) {
        return createErrorResponse('No rotation metadata found in image');
      }
      
      return createSuccessResponse(rotation);
    } catch (error) {
      return createErrorResponse(`Error reading rotation info: ${error instanceof Error ? error.message : String(error)}`);
    }
  }

• src/tools/index.ts:199-221 (registration)

  Registers the 'rotation-info' tool on the MCP server with name, description, input schema, and handler function.

  // Tool 9: rotation-info - gets rotation and flip information
  const rotationInfoTool = server.tool('rotation-info',
    "Get detailed rotation and flip information from image orientation",
    {
      image: ImageSourceSchema
    },
    async (args, extra) => {
      try {
        const { image } = args;
        const buf = await loadImage(image);
        const rotation = await exifr.rotation(buf);
        
        if (!rotation) {
          return createErrorResponse('No rotation metadata found in image');
        }
        
        return createSuccessResponse(rotation);
      } catch (error) {
        return createErrorResponse(`Error reading rotation info: ${error instanceof Error ? error.message : String(error)}`);
      }
    }
  );
  tools['rotation-info'] = rotationInfoTool;

• src/tools/index.ts:54-60 (schema)

  Zod schema defining the input 'image' parameter as ImageSource (path, url, base64, or buffer).

  const ImageSourceSchema = z.object({
    kind: z.enum(['path', 'url', 'base64', 'buffer']),
    path: z.string().optional(),
    url: z.string().optional(),
    data: z.string().optional(),
    buffer: z.string().optional()
  });

• src/tools/loaders.ts:11-72 (helper)

  Helper function to load image data into buffer from various source types, used in the handler.

  export async function loadImage(src: ImageSourceType): Promise<Buffer | Uint8Array> {
    try {
      switch (src.kind) {
        case 'path':
          if (!src.path) {
            throw new Error('Path is required for kind="path"');
          }
          return await fs.promises.readFile(src.path);
        
        case 'url':
          if (!src.url) {
            throw new Error('URL is required for kind="url"');
          }
          
          if (src.url.startsWith('file://')) {
            // Handle file:// URLs by converting to filesystem path
            const filePath = fileURLToPath(src.url);
            return await fs.promises.readFile(filePath);
          } else {
            // Handle HTTP/HTTPS URLs
            const response = await fetch(src.url);
            if (!response.ok) {
              throw new Error(`Failed to fetch URL: ${response.status} ${response.statusText}`);
            }
            return new Uint8Array(await response.arrayBuffer());
          }
        
        case 'base64':
          if (!src.data) {
            throw new Error('Data is required for kind="base64"');
          }
          
          // Check for potential oversized base64 string (>30MB)
          if (src.data.length > 40000000) { // ~30MB in base64
            throw new Error('PayloadTooLarge: Base64 data exceeds 30MB limit');
          }
          
          // Handle data URIs or raw base64
          if (src.data.startsWith('data:')) {
            const base64Data = src.data.split(',')[1];
            return Buffer.from(base64Data, 'base64');
          } else {
            return Buffer.from(src.data, 'base64');
          }
        
        case 'buffer':
          if (!src.buffer) {
            throw new Error('Buffer is required for kind="buffer"');
          }
          return Buffer.from(src.buffer, 'base64');
        
        default:
          // This should never happen due to type constraints, but TypeScript needs it
          throw new Error(`Unsupported image source kind: ${(src as any).kind}`);
      }
    } catch (error) {
      if (error instanceof Error) {
        throw new Error(`Failed to load image: ${error.message}`);
      }
      throw error;
    }
  }