python-sdk/tests/issues/test_355_type_error.py at main · amoycode/python-sdk · GitHub

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from collections.abc import AsyncIterator

from contextlib import asynccontextmanager

from dataclasses import dataclass

from mcp.server.fastmcp import Context, FastMCP

class Database: # Replace with your actual DB type

@classmethod

async def connect(cls):

return cls()

async def disconnect(self):

pass

def query(self):

return "Hello, World!"

# Create a named server

mcp = FastMCP("My App")

@dataclass

class AppContext:

db: Database

@asynccontextmanager

async def app_lifespan(server: FastMCP) -> AsyncIterator[AppContext]:

"""Manage application lifecycle with type-safe context"""

# Initialize on startup

db = await Database.connect()

try:

yield AppContext(db=db)

finally:

# Cleanup on shutdown

await db.disconnect()

# Pass lifespan to server

mcp = FastMCP("My App", lifespan=app_lifespan)

# Access type-safe lifespan context in tools

@mcp.tool()

def query_db(ctx: Context) -> str:

"""Tool that uses initialized resources"""

db = ctx.request_context.lifespan_context.db

return db.query()

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