FastMCP — Build MCP Servers in Python, Fast

Key Features

Simple Decorator API

Define tools, resources, and prompts with Python decorators — no boilerplate:

@mcp.tool()
def search_files(query: str, max_results: int = 10) -> list[str]:
    """Search files matching query."""
    ...

Automatic Type Validation

Uses Pydantic for automatic request/response validation from type hints.

Built-in Testing

from fastmcp.testing import MCPTestClient
async with MCPTestClient(mcp) as client:
    result = await client.call_tool("add", {"a": 1, "b": 2})
    assert result == 3

MCP Client

Also includes a Python MCP client for connecting to any MCP server.

OpenAPI Integration

Import existing OpenAPI/Swagger specs to auto-generate MCP tools from REST APIs.

FAQ

Q: What is FastMCP? A: FastMCP is a Python framework for building MCP servers and clients with a clean decorator API. It handles protocol complexity, type validation, and serialization automatically. 24K+ stars on GitHub.

Q: How is FastMCP different from the official MCP SDK? A: FastMCP provides a higher-level, more Pythonic API with decorators, automatic type validation, built-in testing, and OpenAPI integration — reducing boilerplate significantly.