Quick reference

Value	When it occurs	What to do
end_turn	Claude finished its response naturally.	Use the response.
max_tokens	The response reached your max_tokens limit.	Raise max_tokens or continue the response.
stop_sequence	Claude emitted one of your stop_sequences.	Read stop_sequence to see which one fired.
tool_use	Claude is calling a tool.	Run the tool and return the result. A server tool call still missing its result block completes in a later response.
pause_turn	A server-tool loop reached its iteration limit.	Send the assistant content back to continue.
refusal	Claude declined to respond.	Read stop_details and retry on a fallback model.
model_context_window_exceeded	The response filled the model's context window.	Treat the response as truncated.