FastAPI-MCP — Turn Any FastAPI into MCP Tools

Introduction

FastAPI-MCP is a Python library that automatically converts your existing FastAPI endpoints into MCP-compatible tools. Instead of writing MCP server code from scratch, you add a single line to your existing FastAPI app and every endpoint becomes an AI-callable tool.

Key features:

• Zero Config — FastApiMCP(app).mount() is all you need. Every route becomes an MCP tool automatically.
• Authentication Built-in — Leverages your existing FastAPI security dependencies (OAuth2, API keys, etc.) for MCP tool access.
• Schema Preservation — Request/response models, validation rules, and documentation carry over to MCP tool definitions.
• Selective Exposure — Include or exclude specific endpoints with include_operations and exclude_operations.
• ASGI Transport — Direct in-process communication eliminates HTTP overhead when the MCP client and FastAPI run together.
• Custom Tool Naming — Override auto-generated tool names for cleaner AI assistant integration.

Perfect for teams that already have FastAPI backends and want to make them AI-accessible without rewriting anything.

FAQ

Q: Does it work with existing authentication? A: Yes. FastAPI-MCP reuses your existing FastAPI Depends() security — OAuth2 bearer tokens, API keys, and custom auth all work transparently.

Q: Can I choose which endpoints to expose? A: Yes. Use include_operations=["get_item", "list_items"] or exclude_operations=["delete_all"] to control access.

Q: How do I connect Claude to my FastAPI-MCP server? A: Add this to your MCP config:

{
  "mcpServers": {
    "my-api": {
      "url": "http://localhost:8000/mcp"
    }
  }
}

Q: Does it handle complex request bodies? A: Yes. Pydantic models, query parameters, path parameters, and JSON bodies are all converted to MCP tool input schemas automatically.

Works With

• FastAPI 0.100+
• Python 3.10+
• Claude Code / Claude Desktop / Any MCP client
• Any existing FastAPI authentication setup