Tool call

The model's output naming a tool and its arguments — just structured text. It doesn't do anything on its own; the harness has to read it and execute. Produced by the model in one model provider request.

Usage:

"It said it ran the tests but the file timestamps haven't changed."

"Look at the transcript — did it actually emit a tool call, or just describe running them? The model produces the call, but if the harness didn't execute it, nothing happened."