fastapi-mcp-server ⚡

Turn any FastAPI app into a Claude-compatible MCP server instantly by reading its OpenAPI spec

What it does

Point this tool at any running FastAPI app and it will:

1. Fetch the OpenAPI spec automatically from /openapi.json
2. Parse every endpoint — paths, methods, parameters, request bodies
3. Dynamically register one MCP tool per endpoint
4. Claude can now call any endpoint using natural language

Zero manual tool writing. Zero code changes to your existing FastAPI app.

Demo

User: "Create a task titled Push code to GitHub with high priority"
Claude: [calls post_tasks tool]
        → Task created successfully ✅

User: "Mark task 2 as completed"
Claude: [calls put_tasks_task_id tool]
        → Task updated ✅

User: "Show me all tasks"
Claude: [calls get_tasks tool]
        → Returns all tasks ✅

Architecture

Your FastAPI App (running)
        ↓
fastapi-mcp-server fetches /openapi.json
        ↓
OpenAPIParser extracts all endpoints
        ↓
One MCP tool registered per endpoint
        ↓
Claude calls tools using natural language
        ↓
MCP server makes real HTTP requests to your API
        ↓
Results returned to Claude

Tech Stack

• Python 3.12
• FastAPI + Pydantic
• MCP (Model Context Protocol)
• httpx
• OpenAPI 3.x

Setup

1. Clone and install

git clone https://github.com/vkmech999/fastapi-mcp-server.git
cd fastapi-mcp-server
python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt

2. Configure environment

cp .env.example .env
# Set TARGET_API_URL to your FastAPI app
# Set AUTH_TYPE if your API requires authentication

3. Connect to Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "fastapi-mcp-server": {
      "command": "/path/to/venv/bin/python3",
      "args": ["-m", "mcp_server.server"],
      "env": {
        "TARGET_API_URL": "http://localhost:8000",
        "AUTH_TYPE": "none",
        "PYTHONPATH": "/path/to/fastapi-mcp-server"
      }
    }
  }
}

4. Use it in Claude Desktop

"List all available endpoints"
"Get all tasks"
"Create a new user named John with email john@example.com"
"Delete task with ID 3"

Authentication Support

Auth Type	Use Case	Config
none	Public APIs	AUTH_TYPE=none
bearer	JWT / OAuth2	AUTH_TYPE=bearer + AUTH_TOKEN=eyJ...
api_key	Third-party APIs	AUTH_TYPE=api_key + AUTH_TOKEN=sk-... + AUTH_HEADER=X-API-Key
basic	Legacy systems	AUTH_TYPE=basic + AUTH_USERNAME + AUTH_PASSWORD

MCP Tools

Tool	Description
list_api_endpoints	Discover all registered endpoint tools
get_*	Auto-generated GET endpoint tools
post_*	Auto-generated POST endpoint tools
put_*	Auto-generated PUT endpoint tools
delete_*	Auto-generated DELETE endpoint tools

Running Tests

pytest tests/test_server.py -v

Author

Vivek Kumar — Senior Python Full Stack Developer
LinkedIn · GitHub