Key points
- Each pass has four stages: send the request, inspect
stop_reason, run the requested tools, return the results for the next pass. tool_usemeans keep going;end_turnmeans the task is finished.- Tool results are appended to the message history so the next call can reason about them.
- Claude chooses the next tool from context; a fixed tool sequence or decision tree only fits steps that never vary.
- A reply can contain text and a tool request at the same time, so text alone never means done.
- An iteration cap is a safety net, not the normal way to stop.
Common misconceptions
- "If the reply contains a sentence, Claude is finished." Only the stop reason says that.
- "Sending just the latest message is enough." Without the history Claude repeats lookups and loses earlier findings.
- "A fixed pass limit is a fine stopping rule." It cuts real tasks short and wastes passes on short ones.
Watch for
Loops that end on text content, stop on a pass count, or script the tool order instead of letting the model decide.
Practice Task 1.1
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