docs: stop presenting the in-memory client as the way to connect (#3443)

docs_src/extensions/tutorial004_client.py

@@ -0,0 +1,35 @@
+from typing import Literal
+
+import anyio
+
+import mcp.types as types
+from mcp import Client
+from mcp.client import advertise
+
+EXTENSION_ID = "com.example/search"
+
+
+class SearchParams(types.RequestParams):
+    query: str
+    limit: int = 10
+
+
+class SearchResult(types.Result):
+    items: list[str]
+
+
+class SearchRequest(types.Request[SearchParams, Literal["com.example/search"]]):
+    method: Literal["com.example/search"] = "com.example/search"
+    params: SearchParams
+
+
+async def main() -> None:
+    async with Client("http://localhost:8000/mcp", extensions=[advertise(EXTENSION_ID)]) as client:
+        request = SearchRequest(params=SearchParams(query="mcp", limit=3))
+        result = await client.session.send_request(request, SearchResult)
+        print(result.items)
+        # ['mcp-0', 'mcp-1', 'mcp-2']
+
+
+if __name__ == "__main__":
+    anyio.run(main)