Add a client extension API (#3034)

tests/types/test_request_name_param.py

@@ -0,0 +1,37 @@
+"""`Request.name_param`: the wire-params key a request type declares for `Mcp-Name` emission."""
+
+from typing import Literal
+
+import mcp_types as types
+from mcp_types import CallToolRequest, PingRequest, Request
+
+
+class _VendorParams(types.RequestParams):
+    task_id: str
+
+
+class _VendorRequest(Request[_VendorParams, Literal["vendor/tasks/get"]]):
+    method: Literal["vendor/tasks/get"] = "vendor/tasks/get"
+    name_param = "taskId"
+
+
+def test_request_base_declares_no_name_param() -> None:
+    assert Request.name_param is None
+
+
+def test_core_request_types_inherit_none() -> None:
+    assert CallToolRequest.name_param is None
+    assert PingRequest.name_param is None
+
+
+def test_subclass_overrides_by_bare_assignment() -> None:
+    """Subclasses set `name_param` by bare assignment; the override is class-local."""
+    assert _VendorRequest.name_param == "taskId"
+    assert Request.name_param is None
+
+
+def test_name_param_is_not_a_pydantic_field() -> None:
+    request = _VendorRequest(params=_VendorParams(task_id="t-1"))
+    assert "name_param" not in _VendorRequest.model_fields
+    dumped = request.model_dump(by_alias=True, mode="json", exclude_none=True)
+    assert dumped == {"method": "vendor/tasks/get", "params": {"taskId": "t-1"}}