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

docs_src/structured_output/tutorial007.py

@@ -0,0 +1,21 @@
+import json
+
+from pydantic import BaseModel
+
+from mcp.server import MCPServer
+
+mcp = MCPServer("Weather")
+
+UPSTREAM = {"London": '{"temperature": 16.2, "conditions": "Overcast"}'}
+
+
+class WeatherData(BaseModel):
+    temperature: float
+    humidity: float
+    conditions: str
+
+
+@mcp.tool()
+def get_weather(city: str) -> WeatherData:
+    """Current weather for a city."""
+    return json.loads(UPSTREAM[city])