[Python] Llama Index AgentWorkflow WorkflowRuntimeError: Error in step 'run_agent_step':...

I have a simple llama-index AgentWorkflow based on the first example from this llama-index doc example notebook:

from llama_index.core.agent.workflow import AgentWorkflow
import asyncio

async def magic_number():
"""Get the magic number."""
print("Here")
await asyncio.sleep(1)
return 42

workflow = AgentWorkflow.from_tools_or_functions(
[magic_number],
verbose=True,
llm=llm # <--- Need to define llm for this to run
)

async def main():
result = await workflow.run(user_msg="Get the magic number")
print(result)


if __name__ == "__main__":
asyncio.run(main(), debug=True)


Which produces this error:

Running step init_run
Step init_run produced event AgentInput
Executing <Task pending name='init_run' coro=<Workflow._start.<locals>._task() running at tasks.py:410> took 0.135 seconds
Running step setup_agent
Step setup_agent produced event AgentSetup
Running step run_agent_step
Executing <Task pending name='run_agent_step' coro=<Workflow._start.<locals>._task() running at tasks.py:410> took 0.706 seconds
Exception in callback Dispatcher.span.<locals>.wrapper.<locals>.handle_future_result(span_id='Workflow.run...-e79838aa3b7a', bound_args=<BoundArgumen...mory': None})>, instance=<llama_index....00203B74F7620>, context=<_contextvars...00203B6D93440>)(<WorkflowHand...handler.py:20>) at dispatcher.py:274
handle: <Handle Dispatcher.span.<locals>.wrapper.<locals>.handle_future_result(span_id='Workflow.run...-e79838aa3b7a', bound_args=<BoundArgumen...mory': None})>, instance=<llama_index....00203B74F7620>, context=<_contextvars...00203B6D93440>)(<WorkflowHand...handler.py:20>) at workflow.py:553>
source_traceback: Object created at (most recent call last):
File "test.py", line 36, in <module>
asyncio.run(main(), debug=True)
File "runners.py", line 194, in run
return runner.run(main)
File "runners.py", line 118, in run
return self._loop.run_until_complete(task)
File "base_events.py", line 708, in run_until_complete
self.run_forever()
File "base_events.py", line 679, in run_forever
self._run_once()
File "base_events.py", line 2019, in _run_once
handle._run()
File "events.py", line 89, in _run
self._context.run(self._callback, *self._args)
File "workflow.py", line 553, in _run_workflow
result.set_exception(e)
Traceback (most recent call last):
File "workflow.py", line 304, in _task
new_ev = await instrumented_step(**kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "dispatcher.py", line 368, in async_wrapper
result = await func(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "multi_agent_workflow.py", line 329, in run_agent_step
agent_output = await agent.take_step(
^^^^^^^^^^^^^^^^^^^^^^
...<4 lines>...
)
^
File "function_agent.py", line 48, in take_step
async for last_chat_response in response:
...<16 lines>...
)
File "callbacks.py", line 88, in wrapped_gen
async for x in f_return_val:
...<8 lines>...
last_response = x
File "base.py", line 495, in gen
tool_use = content_block_start["toolUse"]
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^
KeyError: 'toolUse'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "events.py", line 89, in _run
self._context.run(self._callback, *self._args)
~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "dispatcher.py", line 286, in handle_future_result
raise exception
File "workflow.py", line 542, in _run_workflow
raise exception_raised
File "workflow.py", line 311, in _task
raise WorkflowRuntimeError(
f"Error in step '{name}': {e!s}"
) from e
llama_index.core.workflow.errors.WorkflowRuntimeError: Error in step 'run_agent_step': 'toolUse'
Traceback (most recent call last):
File "workflow.py", line 304, in _task
new_ev = await instrumented_step(**kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "dispatcher.py", line 368, in async_wrapper
result = await func(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "multi_agent_workflow.py", line 329, in run_agent_step
agent_output = await agent.take_step(
^^^^^^^^^^^^^^^^^^^^^^
...<4 lines>...
)
^
File "function_agent.py", line 48, in take_step
async for last_chat_response in response:
...<16 lines>...
)
File "callbacks.py", line 88, in wrapped_gen
async for x in f_return_val:
...<8 lines>...
last_response = x
File "base.py", line 495, in gen
tool_use = content_block_start["toolUse"]
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^
KeyError: 'toolUse'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "test.py", line 36, in <module>
asyncio.run(main(), debug=True)
~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
File "runners.py", line 194, in run
return runner.run(main)
~~~~~~~~~~^^^^^^
File "runners.py", line 118, in run
return self._loop.run_until_complete(task)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "base_events.py", line 721, in run_until_complete
return future.result()
~~~~~~~~~~~~~^^
File "test.py", line 31, in main
result = await workflow.run(user_msg="Get the magic number")
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "workflow.py", line 542, in _run_workflow
raise exception_raised
File "workflow.py", line 311, in _task
raise WorkflowRuntimeError(
f"Error in step '{name}': {e!s}"
) from e
llama_index.core.workflow.errors.WorkflowRuntimeError: Error in step 'run_agent_step': 'toolUse'


This should be simpler than the example in the docs, but I keep getting this error. Can anyone help me understand why?

I am running Python 3.13, llama-index 0.12.24.post1, and using LLM anthropic claude 3.5 sonnet.

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