A support agent built with the Agent SDK calls lookup_order with the same order ID three or four times in a row before answering. Logs show each call executes successfully and stop_reason is "tool_use" every time. What is the most likely root cause?

Answer: D — The loop runs the tool but never appends the tool_result to the messages, so the model never sees it

The model can only reason over what's in its context. If the loop executes the tool but doesn't append the tool_result before the next request, the model is choosing blind and asks again. A vague description (a) or prompt wording (c) doesn't explain repeating an identical call; a tighter iteration cap (b) hides the symptom and truncates legitimate work.