MCP Server + AI Agent

A Python MCP server with JWT authentication and sample tools (weather + Bitcoin price), plus an AI agent that uses OpenAI to reason about and call those tools.

Architecture

User prompt → OpenAI GPT-4o (decides tool calls) → MCP Client → MCP Server (localhost:8000)
                    ↑                                    ↓
                    └──────── tool results ──────────────┘

• MCP Server: mcp Python SDK (FastMCP) + Starlette, Streamable HTTP at POST /mcp
• Auth: HS256 JWT — self-signed tokens, validated by the server
• Tools: Auto-discovered via MCP protocol — add tools to the server, agent sees them automatically
• Agent: Interactive CLI that connects to the MCP server and uses OpenAI for reasoning

Project Structure

mcp-server/
├── pyproject.toml
├── Dockerfile
├── .env.example
├── .env                        ← your secrets (git-ignored)
├── scripts/
│   └── generate_token.py       ← mint JWT tokens
├── src/                        ← MCP Server
│   ├── __init__.py
│   ├── config.py               ← loads env vars
│   ├── auth.py                 ← HS256 JWT verifier
│   ├── server.py               ← FastMCP + Starlette app
│   └── tools/
│       ├── __init__.py
│       ├── weather.py          ← Open-Meteo weather tool
│       └── crypto.py           ← CoinGecko Bitcoin price tool
└── agent/                      ← AI Agent
    ├── __init__.py
    ├── mcp_client.py           ← connects to MCP server
    ├── llm.py                  ← OpenAI integration
    └── main.py                 ← interactive CLI

---

Prerequisites

Tool	Install
Python 3.12+	brew install python@3.12
uv (package manager)	brew install uv
Docker (optional)	Docker Desktop for Mac

Setup

1. Install dependencies

cd /path/to/mcp-server
uv sync

This installs all Python packages (mcp, httpx, pyjwt, uvicorn, openai, etc.) into a local .venv.

2. Create your .env file

cp .env.example .env

3. Generate a JWT secret

openssl rand -hex 32

Paste the output as JWT_SECRET in .env.

4. Generate a JWT token

uv run python scripts/generate_token.py

This prints a JWT token valid for 30 days. Paste it as MCP_TOKEN in .env.

Options:

uv run python scripts/generate_token.py --sub amit --days 60

5. Add your API keys to .env

JWT_SECRET=<from step 3>
MCP_SERVER_URL=http://localhost:8000/mcp
MCP_TOKEN=<from step 4>
OPENAI_API_KEY=<your OpenAI API key>

---

MCP Server

Start the server

uv run uvicorn src.server:app --port 8000

The server runs at http://localhost:8000. Press Ctrl+C to stop.

Test the server

Health check

curl http://localhost:8000/health

Expected: {"status":"ok"}

Test unauthenticated access (should be blocked)

curl -s -w "\nHTTP %{http_code}\n" -X POST http://localhost:8000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2025-03-26","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}'

Expected: 401 Unauthorized

Test authenticated access

TOKEN=$(uv run python scripts/generate_token.py)

# Initialize
curl -s -X POST http://localhost:8000/mcp \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2025-03-26","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}' | python3 -m json.tool

Expected: JSON with protocolVersion, capabilities, and serverInfo.

List tools

curl -s -X POST http://localhost:8000/mcp \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","method":"tools/list","id":2}' | python3 -m json.tool

Expected: Two tools — get_weather and get_bitcoin_price with their input schemas.

Call the Bitcoin price tool

curl -s -X POST http://localhost:8000/mcp \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","method":"tools/call","id":3,"params":{"name":"get_bitcoin_price","arguments":{"currency":"usd"}}}' | python3 -m json.tool

Expected: Current Bitcoin price in USD.

Call the weather tool (needs API key)

curl -s -X POST http://localhost:8000/mcp \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","method":"tools/call","id":4,"params":{"name":"get_weather","arguments":{"city":"London"}}}' | python3 -m json.tool

The weather tool uses the free Open-Meteo API — no API key required.

---

AI Agent

The agent connects to the MCP server, auto-discovers tools, and uses OpenAI GPT-4o to decide when to call them.

Run the agent

Make sure the MCP server is running first (in a separate terminal), then:

uv run python -m agent.main

Expected output:

Connecting to MCP server...
Connected to: MCP Server v1.26.0
Available tools: get_weather, get_bitcoin_price

Type your question (or 'quit' to exit):

Example prompts

Prompt	What happens
What's the Bitcoin price?	Agent calls get_bitcoin_price → returns price
What is Bitcoin trading at in EUR?	Agent calls get_bitcoin_price(currency="eur")
What's the weather in London?	Agent calls get_weather(city="London") (needs API key)
What's 2 + 2?	Agent answers directly — no tool call
quit	Exits the agent

Tool calls are visible in real time:

You: What's the Bitcoin price?
  → Calling get_bitcoin_price({"currency": "usd"})
  ← Result received
Assistant: Bitcoin is at $70,487 USD, up 3.3% in the last 24h.

---

MCP Inspector (Debugging UI)

MCP Inspector is the official interactive debugging tool for MCP servers. It provides a web UI to connect, list tools, call them, and inspect raw JSON-RPC messages.

Launch the Inspector

No install needed — run it directly with npx:

npx @modelcontextprotocol/inspector

This opens a web UI at http://localhost:6274.

Connect to Your Server

1. Transport Type: Select Streamable HTTP
2. URL: http://localhost:8000/mcp
3. Authentication: Add a header:
   • Header Name: Authorization
   • Header Value: Bearer <your MCP_TOKEN from .env>

Important: The token value must start with Bearer (with a space) followed by your JWT token.

4. Click Connect

What You Can Do

• List Tools — view all registered tools (get_weather, get_bitcoin_price, etc.)
• Call Tools — fill in arguments and execute tool calls interactively
• Inspect Messages — view raw JSON-RPC request/response traffic
• Test Auth — verify your JWT tokens are working correctly

Stop the Inspector

Press Ctrl+C in the terminal where the inspector is running.

---

Docker (Optional)

Build and run

docker build -t mcp-server .
docker run -p 8000:8000 --env-file .env mcp-server

This builds a container image and runs the server on port 8000. The --env-file .env passes your secrets into the container.

Test

Same curl commands as above — the server is at http://localhost:8000.

---

Expose to Internet (Optional)

Cloudflare Tunnel (no account needed)

brew install cloudflared
cloudflared tunnel --url http://localhost:8000

This gives you a public https://*.trycloudflare.com URL. No signup required. Stop with Ctrl+C.

Cloud Run (Google Cloud)

gcloud run deploy mcp-server --source . --allow-unauthenticated

One command deploy. Tear down with:

gcloud run services delete mcp-server

---

Adding New Tools

1. Create a new file in src/tools/ (e.g. src/tools/my_tool.py)
2. Write an async function with type hints and a docstring:

async def my_tool(param: str) -> dict:
    """Description shown to the LLM."""
    return {"result": "..."}

3. Register it in src/server.py:

from src.tools.my_tool import my_tool
mcp.tool()(my_tool)

4. Restart the server — the agent auto-discovers the new tool on next startup.