If you add endpoints to your FastAPI app after creating the MCP server, you’ll need to refresh the server to include them: 
from fastapi import FastAPI
from fastapi_mcp import FastApiMCP

app = FastAPI()

mcp = FastApiMCP(app)
mcp.mount_http()

# Add new endpoints after MCP server creation
@app.get("/new/endpoint/", operation_id="new_endpoint")
async def new_endpoint():
    return {"message": "Hello, world!"}

# Refresh the MCP server to include the new endpoint
mcp.setup_server()