Serve subscriptions/listen with a pluggable event bus (SEP-2575) (#3035)

docs_src/subscriptions/tutorial002.py

@@ -0,0 +1,40 @@
+from typing import Any
+
+import mcp_types as types
+
+from mcp.server.context import ServerRequestContext
+from mcp.server.lowlevel import Server
+from mcp.server.subscriptions import InMemorySubscriptionBus, ListenHandler, ResourceUpdated
+
+bus = InMemorySubscriptionBus()
+
+NOTES = {"todo": "buy milk"}
+
+EDIT_NOTE_SCHEMA: dict[str, Any] = {
+    "type": "object",
+    "properties": {"name": {"type": "string"}, "text": {"type": "string"}},
+    "required": ["name", "text"],
+}
+
+
+async def list_tools(
+    ctx: ServerRequestContext[Any], params: types.PaginatedRequestParams | None
+) -> types.ListToolsResult:
+    return types.ListToolsResult(
+        tools=[types.Tool(name="edit_note", description="Replace a note's text.", input_schema=EDIT_NOTE_SCHEMA)]
+    )
+
+
+async def call_tool(ctx: ServerRequestContext[Any], params: types.CallToolRequestParams) -> types.CallToolResult:
+    args = params.arguments or {}
+    NOTES[args["name"]] = args["text"]
+    await bus.publish(ResourceUpdated(uri=f"note://{args['name']}"))
+    return types.CallToolResult(content=[types.TextContent(type="text", text="saved")])
+
+
+server = Server(
+    "notebook",
+    on_list_tools=list_tools,
+    on_call_tool=call_tool,
+    on_subscriptions_listen=ListenHandler(bus),
+)