diff --git a/src/google/adk/tools/mcp_tool/mcp_tool.py b/src/google/adk/tools/mcp_tool/mcp_tool.py
index a172b75969..b8d366b6f6 100644
--- a/src/google/adk/tools/mcp_tool/mcp_tool.py
+++ b/src/google/adk/tools/mcp_tool/mcp_tool.py
@@ -72,6 +72,12 @@
     REQUEST_CONFIRMATION_FUNCTION_CALL_NAME,
     REQUEST_INPUT_FUNCTION_CALL_NAME,
     transfer_to_agent.__name__,
+    # Injected by the output-schema processor whenever output_schema is set
+    # alongside other tools (flows/llm_flows/prompt/_schema.py) and read back
+    # by name in base_llm_flow.py, so it is a framework-owned wire name too.
+    # Spelled out because the function is defined inside
+    # SetModelResponseTool.__init__ and is not importable.
+    'set_model_response',
 })
 
 _UNSET = object()
diff --git a/tests/unittests/tools/mcp_tool/test_mcp_tool.py b/tests/unittests/tools/mcp_tool/test_mcp_tool.py
index f1889f1c4a..4f10476aae 100644
--- a/tests/unittests/tools/mcp_tool/test_mcp_tool.py
+++ b/tests/unittests/tools/mcp_tool/test_mcp_tool.py
@@ -344,6 +344,7 @@ def test_init_with_empty_description(self):
           "adk_request_confirmation",
           "adk_request_input",
           "transfer_to_agent",
+          "set_model_response",
       ],
   )
   def test_init_reserved_name(self, reserved_name):
diff --git a/tests/unittests/tools/mcp_tool/test_mcp_toolset.py b/tests/unittests/tools/mcp_tool/test_mcp_toolset.py
index 4dbfdf6c68..2149ef36ae 100644
--- a/tests/unittests/tools/mcp_tool/test_mcp_toolset.py
+++ b/tests/unittests/tools/mcp_tool/test_mcp_toolset.py
@@ -409,6 +409,7 @@ async def test_get_tools_skips_reserved_names(self):
         MockMCPTool("adk_request_credential"),
         MockMCPTool("adk_request_confirmation"),
         MockMCPTool("adk_request_input"),
+        MockMCPTool("set_model_response"),
     ]
     self.mock_session.list_tools = AsyncMock(
         return_value=MockListToolsResult(mock_tools)