FastAPI MCP Server (Single Tool)

A minimal, production-ready MCP server implemented with FastAPI and deployable to Google Cloud Run. It exposes a single tool get_time via the OpenAI Model Context Protocol (MCP) using JSON‑RPC 2.0 over HTTP.

Features

tools/list and tools/call implemented exactly to spec
Returns content (text for humans) and structuredContent (JSON for machines)
Proper JSON‑RPC error codes and input validation with jsonschema
CORS enabled (dev) + optional API key auth via x-api-key
Health check (/healthz) and simple request logging
Dockerfile and one‑command Cloud Run deploy

Endpoints

POST / — JSON‑RPC 2.0 endpoint for tools/list and tools/call
GET /healthz — returns { "ok": true }

Tool

`get_time`

Description: Returns the current UTC timestamp, optionally formatted.

Input schema:

{ "type": "object", "properties": { "format": { "type": "string", "description": "strftime format, e.g. %Y-%m-%dT%H:%M:%SZ" } }, "required": [] }

Output structuredContent:

{ "iso": "2025-01-01T00:00:00Z", "formatted": "optional if format passed" }

Local Dev

python -m venv .venv && source .venv/bin/activate pip install -r requirements.txt uvicorn app:app --reload --port 8000

Test:

curl -s localhost:8000/ -H 'content-type: application/json' -d '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}' | jq curl -s localhost:8000/ -H 'content-type: application/json' -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"get_time","arguments":{"format":"%Y-%m-%dT%H:%M:%SZ"}}}' | jq

If you set API_KEY=secret, include a header: -H 'x-api-key: secret'

Deploy to Google Cloud Run

Option 1 — from source (simplest):

./deploy.sh # Set PROJECT_ID, REGION, SERVICE (or export them)

Option 2 — via Cloud Build pipeline:

gcloud builds submit --project $PROJECT_ID --substitutions=_REGION=us-central1,_SERVICE=mcp-clock

Wire into OpenAI Agent Builder

Add a new MCP Server to your agent
Server URL: your Cloud Run URL (e.g. https://mcp-clock-xxxx-uc.a.run.app)
Label: clock
Allowed tools: get_time (or leave empty to allow all)

License

MIT

This server cannot be installed

-

security - not tested

A

license - permissive license

-

quality - not tested

How are these scores calculated?

Related Resources

GitHub Repository

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FastAPI MCP Server