How AI tool calling works (40 lines of vanilla JavaScript)

Twenty lines of code turn a chat model into an agent. You'll have those twenty lines running today, in JavaScript and in Python, and you'll know what every one of them does. A model can't check the weather, read a file, or send an email. It can only write text. Tool calling is the agreement that turns some of that text into an instruction you agree to carry out. That agreement is the whole of agents. Everything later in this course refines it. No prior agent code assumed, and the exercise runs in the browser tab next to this one.