README - replace code snippets with examples - add lowlevel to snippets (#1150)

examples/snippets/servers/lowlevel/structured_output.py

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+"""
+Run from the repository root:
+    uv run examples/snippets/servers/lowlevel/structured_output.py
+"""
+
+import asyncio
+from typing import Any
+
+import mcp.server.stdio
+import mcp.types as types
+from mcp.server.lowlevel import NotificationOptions, Server
+from mcp.server.models import InitializationOptions
+
+server = Server("example-server")
+
+
+@server.list_tools()
+async def list_tools() -> list[types.Tool]:
+    """List available tools with structured output schemas."""
+    return [
+        types.Tool(
+            name="get_weather",
+            description="Get current weather for a city",
+            inputSchema={
+                "type": "object",
+                "properties": {"city": {"type": "string", "description": "City name"}},
+                "required": ["city"],
+            },
+            outputSchema={
+                "type": "object",
+                "properties": {
+                    "temperature": {"type": "number", "description": "Temperature in Celsius"},
+                    "condition": {"type": "string", "description": "Weather condition"},
+                    "humidity": {"type": "number", "description": "Humidity percentage"},
+                    "city": {"type": "string", "description": "City name"},
+                },
+                "required": ["temperature", "condition", "humidity", "city"],
+            },
+        )
+    ]
+
+
+@server.call_tool()
+async def call_tool(name: str, arguments: dict[str, Any]) -> dict[str, Any]:
+    """Handle tool calls with structured output."""
+    if name == "get_weather":
+        city = arguments["city"]
+
+        # Simulated weather data - in production, call a weather API
+        weather_data = {
+            "temperature": 22.5,
+            "condition": "partly cloudy",
+            "humidity": 65,
+            "city": city,  # Include the requested city
+        }
+
+        # low-level server will validate structured output against the tool's
+        # output schema, and additionally serialize it into a TextContent block
+        # for backwards compatibility with pre-2025-06-18 clients.
+        return weather_data
+    else:
+        raise ValueError(f"Unknown tool: {name}")
+
+
+async def run():
+    """Run the structured output server."""
+    async with mcp.server.stdio.stdio_server() as (read_stream, write_stream):
+        await server.run(
+            read_stream,
+            write_stream,
+            InitializationOptions(
+                server_name="structured-output-example",
+                server_version="0.1.0",
+                capabilities=server.get_capabilities(
+                    notification_options=NotificationOptions(),
+                    experimental_capabilities={},
+                ),
+            ),
+        )
+
+
+if __name__ == "__main__":
+    asyncio.run(run())