FastMCP Demo

A minimal FastMCP demo with stdio and HTTP transports.

uv sync

• server_stdio.py - MCP server (stdio transport), provides add and subtract tools
• server_http.py - MCP server (HTTP transport), provides multiply tool, supports both SSE (legacy) and Streamable HTTP
• test_server.py - Automated tests

# Without HTTP server (in-memory + subprocess)
uv run pytest test_server.py -q -k "not network"

# With Streamable HTTP server (test_http_network)
uv run python server_http.py  # in another terminal
uv run pytest test_server.py -q -k "not sse"

# With SSE server (test_sse_network)
uv run python server_http.py --transport sse  # in another terminal
uv run pytest test_server.py -q

The project includes .mcp.json (project-level config, only works when Claude Code is launched from this directory) with two server configs:

• demo-stdio - Auto-started by Claude Code
• demo-http - Requires manually starting the server first

claude

Once in the session, type /mcp to verify, then test:

Use the add tool to calculate 2 + 3

Start the server first:

# Streamable HTTP (recommended)
uv run python server_http.py

# Or SSE (legacy)
uv run python server_http.py --transport sse

Then in Claude Code:

Use the multiply tool to calculate 2 * 3

Codex CLI supports MCP via global config (~/.codex/config.toml). Project-level config is not yet supported (feature request).

codex mcp add demo-stdio -- uv run python server_stdio.py

# Start server first
uv run python server_http.py

# Add HTTP server with url parameter
codex mcp add demo-http --url http://localhost:8000/mcp

Note: Use --url flag for HTTP servers, not -- with a command. The --url flag tells Codex to connect directly via HTTP.

codex mcp remove demo-stdio
codex mcp remove demo-http

The project includes .gemini/settings.json (project-level config) with two server configs

Usage is similar to Claude Code and Codex CLI.

To make MCP servers available to all projects:

claude mcp add demo-stdio -- uv run python server_stdio.py

To remove:

claude mcp remove demo-stdio