diff --git a/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py b/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
index f7a577af..06d692a2 100644
--- a/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
+++ b/src/google/adk/tools/openapi_tool/openapi_spec_parser/operation_parser.py
@@ -164,8 +164,8 @@ class OperationParser:
   def _process_return_value(self) -> Parameter:
     """Returns a Parameter object representing the return type."""
     responses = self._operation.responses or {}
-    # Default to Any if no 2xx response or if schema is missing
-    return_schema = Schema(type='Any')
+    # Default to empty schema if no 2xx response or if schema is missing
+    return_schema = Schema()
 
     # Take the 20x response with the smallest response code.
     valid_codes = list(