feat: Use json schema for RestApiTool declaration when feature enabled

Co-authored-by: Xuan Yang <xygoogle@google.com>
PiperOrigin-RevId: 855767527

tests/unittests/tools/openapi_tool/openapi_spec_parser/test_rest_api_tool.py

@@ -29,6 +29,8 @@ from google.adk.auth.auth_credential import AuthCredential
 from google.adk.auth.auth_credential import AuthCredentialTypes
 from google.adk.auth.auth_credential import HttpAuth
 from google.adk.auth.auth_credential import HttpCredentials
+from google.adk.features import FeatureName
+from google.adk.features._feature_registry import temporary_feature_override
 from google.adk.sessions.state import State
 from google.adk.tools.openapi_tool.auth.auth_helpers import token_to_scheme_credential
 from google.adk.tools.openapi_tool.common.common import ApiParameter
@@ -204,6 +206,45 @@ class TestRestApiTool:
     assert declaration.description == "Test description"
     assert isinstance(declaration.parameters, Schema)
 
+  def test_get_declaration_with_json_schema_feature_enabled(
+      self, sample_endpoint, sample_operation
+  ):
+    """Test that _get_declaration uses parameters_json_schema when feature is enabled."""
+    mock_parser = MagicMock(spec=OperationParser)
+    mock_parser.get_json_schema.return_value = {
+        "type": "object",
+        "properties": {
+            "test_param": {"type": "string"},
+        },
+        "required": ["test_param"],
+    }
+
+    tool = RestApiTool(
+        name="test_tool",
+        description="Test description",
+        endpoint=sample_endpoint,
+        operation=sample_operation,
+        should_parse_operation=False,
+    )
+    tool._operation_parser = mock_parser
+
+    with temporary_feature_override(
+        FeatureName.JSON_SCHEMA_FOR_FUNC_DECL, True
+    ):
+      declaration = tool._get_declaration()
+
+    assert isinstance(declaration, FunctionDeclaration)
+    assert declaration.name == "test_tool"
+    assert declaration.description == "Test description"
+    assert declaration.parameters is None
+    assert declaration.parameters_json_schema == {
+        "type": "object",
+        "properties": {
+            "test_param": {"type": "string"},
+        },
+        "required": ["test_param"],
+    }
+
   @patch(
       "google.adk.tools.openapi_tool.openapi_spec_parser.rest_api_tool.requests.request"
   )