hermes-agent/optional-skills/mcp/fastmcp/references/fastmcp-cli.md

FastMCP CLI Reference

Use this file when the task needs exact FastMCP CLI workflows rather than the higher-level guidance in SKILL.md.

Install and Verify

pip install fastmcp
fastmcp version

FastMCP documents pip install fastmcp and fastmcp version as the baseline installation and verification path.

Run a Server

Run a server object from a Python file:

fastmcp run server.py:mcp

Run the same server over HTTP:

fastmcp run server.py:mcp --transport http --host 127.0.0.1 --port 8000

Inspect a Server

Inspect what FastMCP will expose:

fastmcp inspect server.py:mcp

This is also the check FastMCP recommends before deploying to Prefect Horizon.

List and Call Tools

List tools from a Python file:

fastmcp list server.py --json

List tools from an HTTP endpoint:

fastmcp list http://127.0.0.1:8000/mcp --json

Call a tool with key-value arguments:

fastmcp call server.py search_resources query=router limit=5 --json

Call a tool with a full JSON input payload:

fastmcp call server.py create_item '{"name": "Widget", "tags": ["sale"]}' --json

Discover Named MCP Servers

Find named servers already configured in local MCP-aware tools:

fastmcp discover

FastMCP documents name-based resolution for Claude Desktop, Claude Code, Cursor, Gemini, Goose, and ./mcp.json.

Install into MCP Clients

Register a server with common clients:

fastmcp install claude-code server.py
fastmcp install claude-desktop server.py
fastmcp install cursor server.py -e .

FastMCP notes that client installs run in isolated environments, so declare dependencies explicitly when needed with flags such as --with, --env-file, or editable installs.

Deployment Checks

Prefect Horizon

Before pushing to Horizon:

fastmcp inspect server.py:mcp

FastMCP’s Horizon docs expect:

• a GitHub repo
• a Python file containing the FastMCP server object
• dependencies declared in requirements.txt or pyproject.toml
• an entrypoint like main.py:mcp

Generic HTTP Hosting

Before shipping to any other host:

1. Start the server locally with HTTP transport.
2. Verify fastmcp list against the local /mcp URL.
3. Verify at least one fastmcp call.
4. Document required environment variables.