FastMCP Configuration Demo

This example demonstrates the recommended way to configure FastMCP servers using fastmcp.json.

Migration from Dependencies Parameter

Previously (deprecated as of FastMCP 2.11.4), you would specify dependencies in the Python code:

mcp = FastMCP("Demo Server", dependencies=["pyautogui", "Pillow"])

Now, dependencies are declared in fastmcp.json:

{
  "environment": {
    "dependencies": ["pyautogui", "Pillow"]
  }
}

Running the Server

With the configuration file in place, you can run the server in several ways:

# Auto-detect fastmcp.json in current directory
cd examples/mcp_server_config_demo
fastmcp run

# Or specify the config file explicitly
fastmcp run examples/mcp_server_config_demo/fastmcp.json

# Or use development mode with the Inspector UI
fastmcp dev examples/mcp_server_config_demo/fastmcp.json

Benefits

• Single source of truth: All configuration in one place
• Environment isolation: Dependencies are installed in an isolated UV environment
• No import-time issues: Dependencies are installed before the server is imported
• IDE support: JSON schema provides autocomplete and validation
• Shareable: Easy to share complete server configuration with others

Configuration Structure

The fastmcp.json file supports three main sections:

1. entrypoint (required): The Python file containing your server
2. environment (optional): Python version and dependencies
3. deployment (optional): Runtime settings like transport and logging

See the full documentation for more details.