Function function_call_round 

fn function_call_round(tool_name: &str, arguments: &str) -> String

A round in which the model calls tool_name with arguments.

Every tool it is used with works without a user, so the round works for an anonymous course material visitor.

The chatbot classifies the round from the function call item it announces and passes the tool parser only what follows that item, so the completed call has to arrive in a later output_item.done, and the round must contain no text delta at all.