Claude Code 🤝 FastMCP

Claude Code supports MCP servers through multiple transport methods including STDIO, SSE, and HTTP, allowing you to extend Claude’s capabilities with custom tools, resources, and prompts from your FastMCP servers.

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Requirements

This integration uses STDIO transport to run your FastMCP server locally. For remote deployments, you can run your FastMCP server with HTTP or SSE transport and configure it directly using Claude Code’s built-in MCP management commands.

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Create a Server

The examples in this guide will use the following simple dice-rolling server, saved as server.py.

import random
from fastmcp import FastMCP

mcp = FastMCP(name="Dice Roller")

@mcp.tool
def roll_dice(n_dice: int) -> list[int]:
    """Roll `n_dice` 6-sided dice and return the results."""
    return [random.randint(1, 6) for _ in range(n_dice)]

if __name__ == "__main__":
    mcp.run()

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Install the Server

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FastMCP CLI

The easiest way to install a FastMCP server in Claude Code is using the fastmcp install claude-code command. This automatically handles the configuration, dependency management, and calls Claude Code’s built-in MCP management system.

fastmcp install claude-code server.py

The install command supports the same file.py:object notation as the run command. If no object is specified, it will automatically look for a FastMCP server object named mcp, server, or app in your file:

# These are equivalent if your server object is named 'mcp'
fastmcp install claude-code server.py
fastmcp install claude-code server.py:mcp

# Use explicit object name if your server has a different name
fastmcp install claude-code server.py:my_custom_server

The command will automatically configure the server with Claude Code’s claude mcp add command.

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Dependencies

If your server has dependencies, include them with the --with flag:

fastmcp install claude-code server.py --with pandas --with requests

Alternatively, you can specify dependencies directly in your server code:

from fastmcp import FastMCP

mcp = FastMCP(
    name="Dice Roller",
    dependencies=["pandas", "requests"]
)

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Environment Variables

If your server needs environment variables (like API keys), you must include them:

fastmcp install claude-code server.py --name "Weather Server" \
  --env-var API_KEY=your-api-key \
  --env-var DEBUG=true

Or load them from a .env file:

fastmcp install claude-code server.py --name "Weather Server" --env-file .env

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Manual Configuration

For more control over the configuration, you can manually use Claude Code’s built-in MCP management commands:

# Add a server with custom configuration
claude mcp add dice-roller -- uv run --with fastmcp fastmcp run server.py

# Add with environment variables
claude mcp add weather-server -e API_KEY=secret -e DEBUG=true -- uv run --with fastmcp fastmcp run server.py

# Add with specific scope (local, user, or project)
claude mcp add my-server --scope user -- uv run --with fastmcp fastmcp run server.py

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Using the Server

Once your server is installed, you can start using your FastMCP server with Claude Code.

Try asking Claude something like:

“Roll some dice for me”

Claude will automatically detect your roll_dice tool and use it to fulfill your request, returning something like:

I’ll roll some dice for you! Here are your results: [4, 2, 6]

You rolled three dice and got a 4, a 2, and a 6!

Claude Code can now access all the tools, resources, and prompts you’ve defined in your FastMCP server.

If your server provides resources, you can reference them with @ mentions using the format @server:protocol://resource/path. If your server provides prompts, you can use them as slash commands with /mcp__servername__promptname.