Preserve Exception in ToolOutput (run-llama#20231)

Author: mauanga

llama-index-core/llama_index/core/agent/workflow/base_agent.py

@@ -301,6 +301,7 @@ async def _call_tool(
                 raw_input=tool_input,
                 raw_output=str(e),
                 is_error=True,
+                exception=e,
             )
 
         return tool_output

llama-index-core/llama_index/core/agent/workflow/multi_agent_workflow.py

@@ -314,6 +314,7 @@ async def _call_tool(
                 raw_input=tool_input,
                 raw_output=str(e),
                 is_error=True,
+                exception=e,
             )
 
         return tool_output

llama-index-core/llama_index/core/tools/calling.py

@@ -29,6 +29,7 @@ def call_tool(tool: BaseTool, arguments: dict) -> ToolOutput:
             raw_input=arguments,
             raw_output=str(e),
             is_error=True,
+            exception=e,
         )
 
 
@@ -55,6 +56,7 @@ async def acall_tool(tool: BaseTool, arguments: dict) -> ToolOutput:
             raw_input=arguments,
             raw_output=str(e),
             is_error=True,
+            exception=e,
         )
 
 

llama-index-core/llama_index/core/tools/types.py

@@ -10,7 +10,7 @@
 if TYPE_CHECKING:
     from llama_index.core.bridge.langchain import StructuredTool, Tool
 from deprecated import deprecated
-from llama_index.core.bridge.pydantic import BaseModel
+from llama_index.core.bridge.pydantic import BaseModel, PrivateAttr
 
 
 class DefaultToolFnSchema(BaseModel):
@@ -99,6 +99,8 @@ class ToolOutput(BaseModel):
     raw_output: Any
     is_error: bool = False
 
+    _exception: Optional[Exception] = PrivateAttr(default=None)
+
     def __init__(
         self,
         tool_name: str,
@@ -107,6 +109,7 @@ def __init__(
         raw_input: Optional[Dict[str, Any]] = None,
         raw_output: Optional[Any] = None,
         is_error: bool = False,
+        exception: Optional[Exception] = None,
     ):
         if content and blocks:
             raise ValueError("Cannot provide both content and blocks.")
@@ -125,6 +128,8 @@ def __init__(
             is_error=is_error,
         )
 
+        self._exception = exception
+
     @property
     def content(self) -> str:
         """Get the content of the tool output."""
@@ -137,6 +142,11 @@ def content(self, content: str) -> None:
         """Set the content of the tool output."""
         self.blocks = [TextBlock(text=content)]
 
+    @property
+    def exception(self) -> Optional[Exception]:
+        """Get the exception of the tool output."""
+        return self._exception
+
     def __str__(self) -> str:
         """String."""
         return self.content

llama-index-core/tests/agent/workflow/test_function_call.py

@@ -9,7 +9,7 @@
 )
 from llama_index.core.llms import ChatMessage
 from llama_index.core.memory import BaseMemory
-from llama_index.core.tools import ToolOutput
+from llama_index.core.tools import FunctionTool, ToolOutput
 from llama_index.core.workflow.context import Context
 from llama_index.core.workflow.events import StopEvent
 
@@ -432,6 +432,31 @@ async def test_aggregate_tool_results_boolean_logic_verification():
         )
 
 
+@pytest.mark.asyncio
+async def test_call_tool_with_exception(mock_context, test_agent):
+    """
+    Test that when a tool raises an exception, _call_tool catches it
+    and returns a ToolOutput with is_error=True and the exception.
+    """
+
+    # Arrange
+    def error_function(x: int) -> str:
+        raise ValueError("This is a test error")
+
+    error_tool = FunctionTool.from_defaults(error_function)
+    tool_input = {"x": 1}
+
+    # Act
+    tool_output = await test_agent._call_tool(mock_context, error_tool, tool_input)
+
+    # Assert
+    assert tool_output.is_error is True
+    assert isinstance(tool_output.exception, ValueError)
+    assert str(tool_output.exception) == "This is a test error"
+    assert tool_output.tool_name == "error_function"
+    assert tool_output.raw_input == tool_input
+
+
 if __name__ == "__main__":
     # Run the tests
     pytest.main([__file__, "-v"])