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fastmcp.cli.cli

FastMCP CLI tools using Cyclopts.

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Functions

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with_argv 

with_argv(args: list[str] | None)
Temporarily replace sys.argv if args provided. This context manager is used at the CLI boundary to inject server arguments when needed, without mutating sys.argv deep in the source loading logic. Args are provided without the script name, so we preserve sys.argv[0] and replace the rest.

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version 

version()
Display version information and platform details.

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dev 

dev(server_spec: str | None = None) -> None
Run an MCP server with the MCP Inspector for development. Args:
  • server_spec: Python file to run, optionally with :object suffix, or None to auto-detect fastmcp.json

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run 

run(server_spec: str | None = None, *server_args: str) -> None
Run an MCP server or connect to a remote one. The server can be specified in several ways:
  1. Module approach: “server.py” - runs the module directly, looking for an object named ‘mcp’, ‘server’, or ‘app’
  2. Import approach: “server.py:app” - imports and runs the specified server object
  3. URL approach: “http://server-url” - connects to a remote server and creates a proxy
  4. MCPConfig file: “mcp.json” - runs as a proxy server for the MCP Servers in the MCPConfig file
  5. FastMCP config: “fastmcp.json” - runs server using FastMCP configuration
  6. No argument: looks for fastmcp.json in current directory
Server arguments can be passed after — : fastmcp run server.py — —config config.json —debug Args:
  • server_spec: Python file, object specification (file:obj), config file, URL, or None to auto-detect

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inspect 

inspect(server_spec: str | None = None) -> None
Inspect an MCP server and display information or generate a JSON report. This command analyzes an MCP server. Without flags, it displays a text summary. Use —format to output complete JSON data. Examples:

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Show text summary

fastmcp inspect server.py

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Output FastMCP format JSON to stdout

fastmcp inspect server.py —format fastmcp

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Save MCP protocol format to file (format required with -o)

fastmcp inspect server.py —format mcp -o manifest.json

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Inspect from fastmcp.json configuration

fastmcp inspect fastmcp.json fastmcp inspect # auto-detect fastmcp.json Args:
  • server_spec: Python file to inspect, optionally with :object suffix, or fastmcp.json

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prepare 

prepare(config_path: Annotated[str | None, cyclopts.Parameter(help='Path to fastmcp.json configuration file')] = None, output_dir: Annotated[str | None, cyclopts.Parameter(help='Directory to create the persistent environment in')] = None, skip_source: Annotated[bool, cyclopts.Parameter(help='Skip source preparation (e.g., git clone)')] = False) -> None
Prepare a FastMCP project by creating a persistent uv environment. This command creates a persistent uv project with all dependencies installed:
  • Creates a pyproject.toml with dependencies from the config
  • Installs all Python packages into a .venv
  • Prepares the source (git clone, download, etc.) unless —skip-source
After running this command, you can use: fastmcp run <config> —project <output-dir> This is useful for:
  • CI/CD pipelines with separate build and run stages
  • Docker images where you prepare during build
  • Production deployments where you want fast startup times