Tool choice
Also called tool_choice
The API setting that says whether Claude may answer in words, must call one of your tools, or must call one tool you name.
When you send Claude tools, one setting decides how free it is to use them. Left on auto, Claude weighs the request and either calls a tool or simply answers. Set to any, it has to call one of your tools, though it still picks which. Name a tool, and it has to call that one.
That's how a pipeline makes one step happen first: force the extraction tool on the first request, then switch back to auto for the turns after it.
For example
An invoice pipeline forces extract_metadata on the first request, so every document starts with that call, then lets Claude choose its next tools freely.
Put it to use
Where you'll meet tool choice in ChatGPT, Gemini and Claude, how to use it there, and the mix-up most people make.
Daily Bytes Plus is in the Android app.