MCP Mobile Server

Instructions

Implementation Reference

• src/tools/ios.ts:540-607 (handler)

  Handler function that validates inputs, performs security and path checks, executes xcrun simctl to take screenshot, verifies file creation, and returns structured result.

  handler: async (args: any) => {
    checkMacOS();
  
    const validation = IosSimulatorScreenshotSchema.safeParse(args);
    if (!validation.success) {
      throw new Error(`Invalid request: ${validation.error.message}`);
    }
  
    const { udid, path: screenshotPath } = validation.data;
  
    // Validate UDID format
    if (!validateUDID(udid)) {
      throw new Error(`Invalid simulator UDID format. UDID must be in format XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX: ${udid}`);
    }
  
    // Validate screenshot path - must be absolute and not contain dangerous patterns
    if (!path.isAbsolute(screenshotPath)) {
      throw new Error(`Screenshot path must be absolute. Path must start with /: ${screenshotPath}`);
    }
  
    // Security check - prevent path traversal and access to sensitive directories
    const normalizedPath = path.normalize(screenshotPath);
    const dangerousPaths = ['/etc', '/usr', '/System', '/private', '/var'];
    if (dangerousPaths.some(dangerous => normalizedPath.startsWith(dangerous))) {
      throw new Error(`Access to this path is not allowed. Path access denied for security reasons: ${normalizedPath}`);
    }
  
    // Ensure file has image extension
    const allowedExtensions = ['.png', '.jpg', '.jpeg'];
    const extension = path.extname(screenshotPath).toLowerCase();
    if (!allowedExtensions.includes(extension)) {
      throw new Error(`Screenshot file must have image extension. Allowed extensions: ${allowedExtensions.join(', ')}. Got: ${extension}`);
    }
  
    // Create directory if it doesn't exist
    const directory = path.dirname(screenshotPath);
    try {
      await fs.mkdir(directory, { recursive: true });
    } catch (mkdirError) {
      throw new Error(`Failed to create screenshot directory: ${mkdirError}`);
    }
  
    const result = await processExecutor.execute('xcrun', ['simctl', 'io', udid, 'screenshot', screenshotPath]);
  
    if (result.exitCode !== 0) {
      throw new Error(`Failed to capture screenshot: ${result.stderr}`);
    }
  
    // Verify screenshot was created
    let fileStats;
    try {
      fileStats = await fs.stat(screenshotPath);
    } catch {
      throw new Error(`Screenshot file was not created. Expected file: ${screenshotPath}`);
    }
  
    return {
      success: true,
      data: {
        udid,
        screenshotPath,
        fileSize: fileStats.size,
        status: 'captured',
        message: 'Screenshot captured successfully',
        output: result.stdout,
      },
    };
  }

• src/tools/ios.ts:70-79 (schema)

  Zod schema used for input validation in the handler, defining udid and path parameters.

   * Zod validation schema for ios_simulator_screenshot tool.
   *
   * @type {z.ZodObject}
   * @property {string} udid - Simulator UDID
   * @property {string} path - Output file path for screenshot
   */
  const IosSimulatorScreenshotSchema = z.object({
    udid: z.string().min(1),
    path: z.string().min(1),
  });

• src/tools/ios.ts:529-608 (registration)

  Registration of the tool in the createIOSTools function, including name, description, inputSchema (JSON schema for MCP), and reference to handler.

  tools.set('ios_take_screenshot', {
    name: 'ios_take_screenshot',
    description: 'Take a screenshot of an iOS simulator',
    inputSchema: {
      type: 'object',
      properties: {
        udid: { type: 'string', minLength: 1, description: 'Simulator UDID' },
        path: { type: 'string', minLength: 1, description: 'Absolute path to save screenshot' }
      },
      required: ['udid', 'path']
    },
    handler: async (args: any) => {
      checkMacOS();
  
      const validation = IosSimulatorScreenshotSchema.safeParse(args);
      if (!validation.success) {
        throw new Error(`Invalid request: ${validation.error.message}`);
      }
  
      const { udid, path: screenshotPath } = validation.data;
  
      // Validate UDID format
      if (!validateUDID(udid)) {
        throw new Error(`Invalid simulator UDID format. UDID must be in format XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX: ${udid}`);
      }
  
      // Validate screenshot path - must be absolute and not contain dangerous patterns
      if (!path.isAbsolute(screenshotPath)) {
        throw new Error(`Screenshot path must be absolute. Path must start with /: ${screenshotPath}`);
      }
  
      // Security check - prevent path traversal and access to sensitive directories
      const normalizedPath = path.normalize(screenshotPath);
      const dangerousPaths = ['/etc', '/usr', '/System', '/private', '/var'];
      if (dangerousPaths.some(dangerous => normalizedPath.startsWith(dangerous))) {
        throw new Error(`Access to this path is not allowed. Path access denied for security reasons: ${normalizedPath}`);
      }
  
      // Ensure file has image extension
      const allowedExtensions = ['.png', '.jpg', '.jpeg'];
      const extension = path.extname(screenshotPath).toLowerCase();
      if (!allowedExtensions.includes(extension)) {
        throw new Error(`Screenshot file must have image extension. Allowed extensions: ${allowedExtensions.join(', ')}. Got: ${extension}`);
      }
  
      // Create directory if it doesn't exist
      const directory = path.dirname(screenshotPath);
      try {
        await fs.mkdir(directory, { recursive: true });
      } catch (mkdirError) {
        throw new Error(`Failed to create screenshot directory: ${mkdirError}`);
      }
  
      const result = await processExecutor.execute('xcrun', ['simctl', 'io', udid, 'screenshot', screenshotPath]);
  
      if (result.exitCode !== 0) {
        throw new Error(`Failed to capture screenshot: ${result.stderr}`);
      }
  
      // Verify screenshot was created
      let fileStats;
      try {
        fileStats = await fs.stat(screenshotPath);
      } catch {
        throw new Error(`Screenshot file was not created. Expected file: ${screenshotPath}`);
      }
  
      return {
        success: true,
        data: {
          udid,
          screenshotPath,
          fileSize: fileStats.size,
          status: 'captured',
          message: 'Screenshot captured successfully',
          output: result.stdout,
        },
      };
    }
  });

• src/tools/ios.ts:159-162 (helper)

  Helper function to validate UDID format, used in the handler.

  const validateUDID = (udid: string): boolean => {
    const uuidPattern = /^[A-F0-9]{8}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{4}-[A-F0-9]{12}$/i;
    return uuidPattern.test(udid);
  };

• src/tools/ios.ts:140-144 (helper)

  Helper function to ensure running on macOS, called at start of handler.

  const checkMacOS = (): void => {
    if (process.platform !== 'darwin') {
      throw new Error(`iOS development tools only work on macOS. Current platform: ${process.platform}`);
    }
  };