fix: refuse the reserved tool name set_model_response

Merge #7145

Fixes #7144

PiperOrigin-RevId: 992443492

Author: sushant-me

src/google/adk/cli/agent_test_runner.py

@@ -35,6 +35,7 @@
 from google.adk.models.llm_response import LlmResponse
 from google.adk.runners import Runner
 from google.adk.sessions.in_memory_session_service import InMemorySessionService
+from google.adk.tools.set_model_response_tool import SetModelResponseTool
 from google.genai import types
 from pydantic import alias_generators
 import pytest
@@ -532,7 +533,7 @@ def test_agent_replay(agent_dir, test_file, monkeypatch):
           for part in parts:
             if "functionResponse" in part:
               func_resp = part["functionResponse"]
-              if func_resp.get("name") == "set_model_response":
+              if func_resp.get("name") == SetModelResponseTool.NAME:
                 last_was_set_model_response = True
 
         elif role == "model":

src/google/adk/flows/llm_flows/prompt/_schema.py

@@ -112,7 +112,7 @@ def get_structured_model_response(function_response_event: Event) -> str | None:
     return None
 
   for func_response in function_response_event.get_function_responses():
-    if func_response.name == 'set_model_response':
+    if func_response.name == SetModelResponseTool.NAME:
       response = function_response_event.actions.set_model_response
       if response is None:
         return None

src/google/adk/tools/mcp_tool/mcp_tool.py

@@ -60,6 +60,7 @@
 # part of the ADK public API; consumers flip the env var, not the symbol.
 from .._gemini_schema_util import _to_gemini_schema
 from ..base_authenticated_tool import BaseAuthenticatedTool
+from ..set_model_response_tool import SetModelResponseTool
 from ..tool_context import ToolContext
 from ..transfer_to_agent_tool import transfer_to_agent
 from .mcp_session_manager import _http_debug_var
@@ -81,6 +82,7 @@
     REQUEST_CONFIRMATION_FUNCTION_CALL_NAME,
     REQUEST_INPUT_FUNCTION_CALL_NAME,
     transfer_to_agent.__name__,
+    SetModelResponseTool.NAME,
 })
 
 _UNSET = object()

src/google/adk/tools/set_model_response_tool.py

@@ -20,6 +20,7 @@
 import types as typing_types
 from typing import Any
 from typing import cast
+from typing import Final
 from typing import get_args
 from typing import get_origin
 from typing import Optional
@@ -112,6 +113,9 @@ def _apply_nested_descriptions(prop: types.Schema, annotation: Any) -> None:
         _apply_nested_descriptions(prop, arg)
 
 
+_SET_MODEL_RESPONSE_TOOL_NAME: Final[str] = 'set_model_response'
+
+
 class SetModelResponseTool(BaseTool):
   """Internal tool used for output schema workaround.
 
@@ -120,6 +124,8 @@ class SetModelResponseTool(BaseTool):
   provide its final structured response instead of outputting text directly.
   """
 
+  NAME: Final[str] = _SET_MODEL_RESPONSE_TOOL_NAME
+
   def __init__(self, output_schema: SchemaType):
     """Initialize the tool with the expected output schema.
 
@@ -213,9 +219,10 @@ def set_model_response() -> str:
     setattr(set_model_response, '__signature__', new_sig)
 
     self.func = set_model_response
+    self.func.__name__ = self.NAME
 
     super().__init__(
-        name=self.func.__name__,
+        name=self.NAME,
         description=self.func.__doc__.strip() if self.func.__doc__ else '',
     )
 

tests/unittests/tools/mcp_tool/test_mcp_tool.py

@@ -46,6 +46,7 @@
 from google.adk.tools.mcp_tool.mcp_tool import MCPTool
 from google.adk.tools.mcp_tool.mcp_tool import ProgressCallbackFactory
 from google.adk.tools.mcp_tool.mcp_tool import ProgressFnT
+from google.adk.tools.set_model_response_tool import SetModelResponseTool
 from google.adk.tools.tool_context import ToolContext
 from google.genai.types import FunctionDeclaration
 from google.genai.types import GroundingMetadata
@@ -734,6 +735,7 @@ def test_init_with_empty_description(self):
           "adk_request_confirmation",
           "adk_request_input",
           "transfer_to_agent",
+          SetModelResponseTool.NAME,
       ],
   )
   def test_init_reserved_name(self, reserved_name):

tests/unittests/tools/mcp_tool/test_mcp_toolset.py

@@ -47,6 +47,7 @@
 from google.adk.tools.mcp_tool.mcp_tool import MCPTool
 from google.adk.tools.mcp_tool.mcp_toolset import McpToolset
 from google.adk.tools.mcp_tool.mcp_toolset import McpToolsetConfig
+from google.adk.tools.set_model_response_tool import SetModelResponseTool
 from google.adk.tools.tool_configs import ToolArgsConfig
 from mcp import StdioServerParameters
 from mcp.types import BlobResourceContents
@@ -409,6 +410,7 @@ async def test_get_tools_skips_reserved_names(self):
         MockMCPTool("adk_request_credential"),
         MockMCPTool("adk_request_confirmation"),
         MockMCPTool("adk_request_input"),
+        MockMCPTool(SetModelResponseTool.NAME),
     ]
     self.mock_session.list_tools = AsyncMock(
         return_value=MockListToolsResult(mock_tools)

tests/unittests/tools/test_set_model_response_tool.py

@@ -70,6 +70,8 @@ def test_tool_initialization_simple_schema():
 
   assert tool.output_schema == PersonSchema
   assert tool.name == 'set_model_response'
+  assert tool.name == SetModelResponseTool.NAME
+  assert tool.func.__name__ == SetModelResponseTool.NAME
   assert 'Set your final response' in tool.description
   assert tool.func is not None