Keep the tutorial handler a plain function with a separate state holder

Author: maxisbey

docs/advanced/caching.md

@@ -39,7 +39,7 @@ One caveat on paginated lists: the protocol requires the **same `cacheScope` on
 
 On a 2026-07-28 session, `Client` honors the hints for you: it has a built-in response cache, on by default. A result that arrives carrying a `ttlMs` is stored, and an identical call within that TTL is served from the cache with no round trip. A result that carries *no* hint is not cached: hint-less results get `CacheConfig.default_ttl_ms`, which defaults to `0` (immediately stale), so a server that declares nothing sees exactly the call-for-call traffic it always did.
 
-```python title="client.py" hl_lines="32 34 37"
+```python title="client.py" hl_lines="33 35 38"
 --8<-- "docs_src/caching/tutorial003.py"
 ```
 

docs_src/caching/tutorial003.py

@@ -9,30 +9,31 @@
 
 
 @dataclass
-class Demo:
+class DemoState:
     fetches: int = 0
     now: float = 1_000_000.0
 
-    async def list_tools(
-        self, ctx: ServerRequestContext[Any], params: PaginatedRequestParams | None
-    ) -> ListToolsResult:
-        self.fetches += 1
-        return ListToolsResult(tools=[Tool(name="forecast", input_schema={"type": "object"})])
+
+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"})])
 
 
-demo = Demo()
 server = Server(
     "Weather",
-    on_list_tools=demo.list_tools,
+    on_list_tools=list_tools,
     cache_hints={"tools/list": CacheHint(ttl_ms=60_000, scope="public")},
 )
 
 
 async def main() -> None:
-    async with Client(server, cache=CacheConfig(clock=lambda: demo.now)) as client:
+    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
-        demo.now += 60.0
+        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, {demo.fetches} fetches")
+        print(f"4 calls, {state.fetches} fetches")