extension.mcpb (ZIP archive)
├── manifest.json         # Extension metadata and configuration
├── server/               # MCP server implementation
│   └── [server files]    
├── dependencies/         # All required packages/libraries
└── icon.png             # Optional: Extension icon

# Example: Node.js Extension
extension.mcpb
├── manifest.json         # Required: Extension metadata and configuration
├── server/               # Server files
│   └── index.js          # Main entry point
├── node_modules/         # Bundled dependencies
├── package.json          # Optional: NPM package definition
└── icon.png              # Optional: Extension icon

# Example: Python Extension
extension.mcpb (ZIP file)
├── manifest.json         # Required: Extension metadata and configuration
├── server/               # Server files
│   ├── main.py           # Main entry point
│   └── utils.py          # Additional modules
├── lib/                  # Bundled Python packages
├── requirements.txt      # Optional: Python dependencies list
└── icon.png              # Optional: Extension icon

{
  "mcpb_version": "0.1",
  "name": "my-extension",
  "version": "1.0.0",
  "description": "A simple MCP extension",
  "author": {
    "name": "Extension Author"
  },
  "server": {
    "type": "node",
    "entry_point": "server/index.js",
    "mcp_config": {
      "command": "node",
      "args": [
        "${__dirname}/server/index.js"
      ]
    }
  }
}

{
  "mcpb_version": "0.1",
  "name": "my-extension",
  "version": "1.0.0",
  "description": "A simple MCP extension",
  "author": {
    "name": "Extension Author"
  },
  "server": {
    "type": "node",
    "entry_point": "server/index.js",
    "mcp_config": {
      "command": "node",
      "args": ["${__dirname}/server/index.js"],
      "env": {
        "API_KEY": "${user_config.api_key}"
      }
    }
  },
  "user_config": {
    "api_key": {
      "type": "string",
      "title": "API Key",
      "description": "Your API key for authentication",
      "sensitive": true,
      "required": true
    }
  }
}

{
  "mcpb_version": "0.1",
  "name": "My MCP Extension",
  "display_name": "My Awesome MCP Extension",
  "version": "1.0.0",
  "description": "A brief description of what this extension does",
  "long_description": "A detailed description that can include multiple paragraphs explaining the extension's functionality, use cases, and features. It supports basic markdown.",
  "author": {
    "name": "Your Name",
    "email": "[email protected]",
    "url": "https://your-website.com"
  },
  "repository": {
    "type": "git",
    "url": "https://github.com/your-username/my-mcp-extension"
  },
  "homepage": "https://example.com/my-extension",
  "documentation": "https://docs.example.com/my-extension",
  "support": "https://github.com/your-username/my-extension/issues",
  "icon": "icon.png",
  "screenshots": [
    "assets/screenshots/screenshot1.png",
    "assets/screenshots/screenshot2.png"
  ],
  "server": {
    "type": "node",
    "entry_point": "server/index.js",
    "mcp_config": {
      "command": "node",
      "args": ["${__dirname}/server/index.js"],
      "env": {
        "ALLOWED_DIRECTORIES": "${user_config.allowed_directories}"
      }
    }
  },
  "tools": [
    {
      "name": "search_files",
      "description": "Search for files in a directory"
    }
  ],
  "prompts": [
    {
      "name": "poetry",
      "description": "Have the LLM write poetry",
      "arguments": ["topic"],
      "text": "Write a creative poem about the following topic: ${arguments.topic}"
    }
  ],
  "tools_generated": true,
  "keywords": ["api", "automation", "productivity"],
  "license": "MIT",
  "compatibility": {
    "claude_desktop": ">=1.0.0",
    "platforms": ["darwin", "win32", "linux"],
    "runtimes": {
      "node": ">=16.0.0"
    }
  },
  "user_config": {
    "allowed_directories": {
      "type": "directory",
      "title": "Allowed Directories",
      "description": "Directories the server can access",
      "multiple": true,
      "required": true,
      "default": ["${HOME}/Desktop"]
    },
    "api_key": {
      "type": "string",
      "title": "API Key",
      "description": "Your API key for authentication",
      "sensitive": true,
      "required": false
    },
    "max_file_size": {
      "type": "number",
      "title": "Maximum File Size (MB)",
      "description": "Maximum file size to process",
      "default": 10,
      "min": 1,
      "max": 100
    }
  }
}

npx @anthropic-ai/mcpb init

"user_config": {
  "allowed_directories": {
    "type": "directory",
    "title": "Allowed Directories",
    "description": "Directories the server can access",
    "multiple": true,
    "required": true,
    "default": ["${HOME}/Documents"]
  }
}

"server": {
   "type": "node",
   "entry_point": "server/index.js",
   "mcp_config": {
   "command": "node",
   "args": ["${__dirname}/server/index.js"],
   "env": {
      "ALLOWED_DIRECTORIES": "${user_config.allowed_directories}"
   }
   }
}

npx @anthropic-ai/mcpb pack

"server": {
  "type": "node",
  "entry_point": "server/index.js",
  "mcp_config": {
    "command": "node",
    "args": ["${__dirname}/server/index.js"],
    "platforms": {
      "win32": {
        "command": "node.exe",
        "env": {
          "TEMP_DIR": "${TEMP}"
        }
      },
      "darwin": {
        "env": {
          "TEMP_DIR": "${TMPDIR}"
        }
      }
    }
  }
}

"tools": [
  {
    "name": "read_file",
    "description": "Read contents of a file"
  }
],
"prompts": [
  {
    "name": "code_review",
    "description": "Review code for best practices",
    "arguments": ["file_path"]
  }
]

npm install -g @anthropic-ai/mcpb
mcpb init
mcpb pack

I want to build this as a Desktop Extension, abbreviated as "MCPB". Please follow these steps:

1. **Read the specifications thoroughly:**
   - https://github.com/anthropics/mcpb/blob/main/README.md - MCPB architecture overview, capabilities, and integration patterns
   - https://github.com/anthropics/mcpb/blob/main/MANIFEST.md - Complete extension manifest structure and field definitions
   - https://github.com/anthropics/mcpb/tree/main/examples - Reference implementations including a "Hello World" example

2. **Create a proper extension structure:**
   - Generate a valid manifest.json following the MANIFEST.md spec
   - Implement an MCP server using @modelcontextprotocol/sdk with proper tool definitions
   - Include proper error handling and timeout management

3. **Follow best development practices:**
   - Implement proper MCP protocol communication via stdio transport
   - Structure tools with clear schemas, validation, and consistent JSON responses
   - Make use of the fact that this extension will be running locally
   - Add appropriate logging and debugging capabilities
   - Include proper documentation and setup instructions

4. **Test considerations:**
   - Validate that all tool calls return properly structured responses
   - Verify manifest loads correctly and host integration works

Generate complete, production-ready code that can be immediately tested. Focus on defensive programming, clear error messages, and following the exact
MCPB specifications to ensure compatibility with the ecosystem.