MCP with FastAPI Infrastructure

An existing ASGI application can host normal HTTP APIs and MCP while sharing the same domain services, database pool, HTTP clients, auth logic, and tracing.

Share services, not endpoints

REST routes ─┐
             ├─ Domain services ─ DB/APIs
MCP tools ───┘

Lifespan

Initialize pools and clients once. Closing and reopening a database pool per tool call creates unnecessary latency and connection pressure.

Policy boundaries

REST middleware assumptions may not map exactly to MCP. Verify authenticated caller context reaches every MCP capability and do not bypass domain authorization.