from dataclasses import dataclass

from typing import Any

from mcp import Client

from mcp.client import CacheConfig

from mcp.server import CacheHint, Server, ServerRequestContext

from mcp.types import ListToolsResult, PaginatedRequestParams, Tool

@dataclass

class DemoState:

fetches: int = 0

now: float = 1_000_000.0

state = DemoState()

async def list_tools(ctx: ServerRequestContext[Any], params: PaginatedRequestParams | None) -> ListToolsResult:

state.fetches += 1

return ListToolsResult(tools=[Tool(name="forecast", input_schema={"type": "object"})])

server = Server(

"Weather",

on_list_tools=list_tools,

cache_hints={"tools/list": CacheHint(ttl_ms=60_000, scope="public")},

)

async def main() -> None:

start = state.fetches

async with Client(server, cache=CacheConfig(clock=lambda: state.now)) as client:

await client.list_tools() # fetch 1

await client.list_tools() # fresh for 60s: served from the cache

state.now += 60.0

await client.list_tools() # the TTL ran out: fetch 2

await client.list_tools(cache_mode="refresh") # skip the cache read: fetch 3

print(f"4 calls, {state.fetches - start} fetches")