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

examples/stories/subscriptions/server.py

@@ -0,0 +1,41 @@
+"""A notebook whose edits and tool changes reach `subscriptions/listen` streams."""
+
+from mcp.server.mcpserver import Context, MCPServer
+from stories._hosting import run_server_from_args
+
+
+def build_server() -> MCPServer:
+    mcp = MCPServer("subscriptions-example")
+    notes = {"todo": "buy milk", "journal": "day one"}
+
+    @mcp.resource("note://{name}")
+    def note(name: str) -> str:
+        return notes[name]
+
+    @mcp.tool()
+    async def edit_note(name: str, text: str, ctx: Context) -> str:
+        """Replace a note's text and tell subscribers that URI changed."""
+        notes[name] = text
+        await ctx.notify_resource_updated(f"note://{name}")
+        return "saved"
+
+    def search(query: str) -> list[str]:
+        return [name for name, text in notes.items() if query in text]
+
+    enabled = False
+
+    @mcp.tool()
+    async def enable_search(ctx: Context) -> str:
+        """Register the `search` tool at runtime and tell subscribers the list changed."""
+        nonlocal enabled
+        if not enabled:
+            enabled = True
+            mcp.add_tool(search)
+            await ctx.notify_tools_changed()
+        return "search is live"
+
+    return mcp
+
+
+if __name__ == "__main__":
+    run_server_from_args(build_server)