fix: prevent result_as_answer from returning error as final answer

When a tool with result_as_answer=True raises an exception, the agent
was receiving result_as_answer=True and returning the error string as
the final answer. Now we set result_as_answer=False when an error event
is emitted, allowing the agent to reflect and retry.

Fixes crewAIInc/crewAI#5156

---------

Co-authored-by: NIK-TIGER-BILL <nik.tiger.bill@github.com>
Co-authored-by: Greyson LaLonde <greyson.r.lalonde@gmail.com>

lib/crewai/src/crewai/utilities/agent_utils.py

@@ -1592,11 +1592,11 @@ def execute_single_native_tool_call(
             color="green",
         )
 
-    # Check result_as_answer
     is_result_as_answer = bool(
         original_tool
         and hasattr(original_tool, "result_as_answer")
         and original_tool.result_as_answer
+        and not error_event_emitted
     )
 
     return NativeToolCallResult(

lib/crewai/tests/utilities/test_agent_utils.py

@@ -17,6 +17,8 @@ from crewai.utilities.agent_utils import (
     _format_messages_for_summary,
     _split_messages_into_chunks,
     convert_tools_to_openai_schema,
+    execute_single_native_tool_call,
+    NativeToolCallResult,
     parse_tool_call_args,
     summarize_messages,
 )
@@ -1033,3 +1035,46 @@ class TestParseToolCallArgs:
         _, error = parse_tool_call_args("{bad json}", "tool", "call_7")
         assert error is not None
         assert set(error.keys()) == {"call_id", "func_name", "result", "from_cache", "original_tool"}
+
+
+class TestExecuteSingleNativeToolCall:
+    """Tests for execute_single_native_tool_call."""
+
+    def test_result_as_answer_false_on_tool_error(self) -> None:
+        """When a tool with result_as_answer=True raises, result_as_answer must be False.
+
+        Regression test for https://github.com/crewAIInc/crewAI/issues/5156
+        """
+        from unittest.mock import MagicMock
+
+        class FailingTool(BaseTool):
+            name: str = "failing_tool"
+            description: str = "A tool that always fails"
+            result_as_answer: bool = True
+
+            def _run(self, **kwargs: Any) -> str:
+                raise RuntimeError("intentional failure")
+
+        tool = FailingTool()
+        tool_call = MagicMock()
+        tool_call.id = "call_1"
+        tool_call.function.name = "failing_tool"
+        tool_call.function.arguments = "{}"
+
+        result = execute_single_native_tool_call(
+            tool_call,
+            available_functions={"failing_tool": tool._run},
+            original_tools=[tool],
+            structured_tools=None,
+            tools_handler=None,
+            agent=None,
+            task=None,
+            crew=None,
+            event_source=MagicMock(),
+            printer=None,
+            verbose=False,
+        )
+
+        assert isinstance(result, NativeToolCallResult)
+        assert result.result_as_answer is False
+        assert "Error executing tool" in result.result