Proton Drive MCP

Instructions

Implementation Reference

• src/index.ts:307-333 (handler)

  The main handler logic for the 'read_file' tool. It validates the input path, checks if the target is a file (not directory), reads the file content using Node.js fs/promises.readFile, and returns it as MCP text content block. Errors are handled with McpError.

  case 'read_file': {
    const readPath = validatePath(args?.path as string);
    
    try {
      // Check if it's a file
      const stats = await stat(readPath);
      if (stats.isDirectory()) {
        throw new Error('Cannot read a directory');
      }
      
      // Read the file
      const content = await readFile(readPath, 'utf-8');
      return {
        content: [
          {
            type: 'text',
            text: content,
          },
        ],
      };
    } catch (error: any) {
      throw new McpError(
        ErrorCode.InternalError,
        `Cannot read file: ${error.message}`
      );
    }
  }

• src/index.ts:148-157 (schema)

  Input schema definition for the 'read_file' tool, specifying an object with a required 'path' string property.

  inputSchema: {
    type: 'object',
    properties: {
      path: { 
        type: 'string', 
        description: 'File path relative to Proton Drive root' 
      },
    },
    required: ['path'],
  },

• src/index.ts:145-158 (registration)

  Registration of the 'read_file' tool in the ListTools response, including name, description, and input schema.

  {
    name: 'read_file',
    description: 'Read a text file from Proton Drive',
    inputSchema: {
      type: 'object',
      properties: {
        path: { 
          type: 'string', 
          description: 'File path relative to Proton Drive root' 
        },
      },
      required: ['path'],
    },
  },

• src/index.ts:91-111 (helper)

  Helper function used by read_file (and other tools) to validate and resolve relative paths to absolute paths within the Proton Drive root, preventing path traversal attacks.

  function validatePath(relativePath: string): string {
    // Handle empty path
    if (!relativePath) {
      return PROTON_DRIVE_PATH;
    }
    
    // Clean the path - remove leading slashes and normalize
    const cleaned = relativePath
      .split(/[/\\]+/)
      .filter(Boolean)
      .join(sep);
    
    const fullPath = resolve(PROTON_DRIVE_PATH, cleaned);
    
    // Security check - ensure we're still within Proton Drive
    if (!fullPath.startsWith(PROTON_DRIVE_PATH)) {
      throw new Error('Invalid path: Access denied outside Proton Drive');
    }
    
    return fullPath;
  }