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

docs_src/extensions/tutorial006_client.py

@@ -0,0 +1,40 @@
+from collections.abc import Sequence
+from typing import Any, Literal
+
+import anyio
+
+import mcp.types as types
+from mcp import Client
+from mcp.client import ClaimContext, ClientExtension, ResultClaim
+
+EXTENSION_ID = "com.example/receipts"
+
+
+class ReceiptResult(types.Result):
+    """The claimed result shape; `result_type` pins the wire tag."""
+
+    result_type: Literal["receipt"] = "receipt"
+    receipt_token: str
+
+
+class Receipts(ClientExtension):
+    """Client half: claims the `receipt` shape and supplies the code that finishes it."""
+
+    identifier = EXTENSION_ID
+
+    def claims(self) -> Sequence[ResultClaim[Any]]:
+        return [ResultClaim(result_type="receipt", model=ReceiptResult, resolve=self._redeem)]
+
+    async def _redeem(self, claimed: ReceiptResult, ctx: ClaimContext) -> types.CallToolResult:
+        return await ctx.session.call_tool("redeem", {"token": claimed.receipt_token})
+
+
+async def main() -> None:
+    async with Client("http://localhost:8000/mcp", extensions=[Receipts()]) as client:
+        result = await client.call_tool("buy", {"item": "lamp"})
+        print(result.content)
+        # [TextContent(type='text', text='goods for r-117', annotations=None, meta=None)]
+
+
+if __name__ == "__main__":
+    anyio.run(main)