Tool use
Also called tool call, function calling
When a model asks the app to run something for it, such as a search, code or another app, and then uses the result.
A model on its own can only write text. Tool use lets it do more: it writes a request ("search for this", "run this code", "read this calendar"), the app carries it out, and the result goes back to the model to use in its answer.
This is how chatbots search the web, do exact maths by running code, read your files and, as agents, click through websites. It's also the honest way to check what happened. When an AI says it looked something up or ran the numbers, the tool step should be visible in the app: a search, a code block, a list of sources. No visible tool use usually means no real lookup.
For example
Asked to add up 47 expenses from a spreadsheet, a chatbot that runs code gets the exact total; one that works it out in its head can be a few pounds off.
Put it to use
Where you'll meet tool use 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.