Rebuild the docs around tested examples; shrink README.v2.md to a pitch (#2978)

docs_src/structured_output/tutorial009.py

@@ -0,0 +1,15 @@
+from mcp.server import MCPServer
+
+mcp = MCPServer("Weather")
+
+
+class Station:
+    def __init__(self, name: str, online: bool):
+        self.name = name
+        self.online = online
+
+
+@mcp.tool()
+def get_station(name: str) -> Station:
+    """Look up a weather station by name."""
+    return Station(name=name, online=True)