Is lifespan ready for the MCP (high-level) server?

[KokoiRuby]

Hello,

I'm new to the MCP. I followed this section in README.md. However, I'm not able to extract anything from the context.

I simply remove the depdency of fake_database, and made db just a string.

# Add lifespan support for startup/shutdown with strong typing
from contextlib import asynccontextmanager
from collections.abc import AsyncIterator
from dataclasses import dataclass
from mcp.server.fastmcp import Context, FastMCP

# Create a named server
mcp = FastMCP("My App")


@dataclass
class AppContext:
    db: str


@asynccontextmanager
async def app_lifespan(server: FastMCP) -> AsyncIterator[AppContext]:
    """Manage application lifecycle with type-safe context"""
    # Initialize on startup
    db = "test str"
    try:
        yield AppContext(db=db)
    finally:
        # Cleanup on shutdown
        ...


# 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

[KokoiRuby]

ummm, probably I need to implement __getitem__() method for the dataclass.

[KokoiRuby]

OK, I've fixed by adding None type checking to the code.