Tool calls.

A tool call is the AI agent actually doing something instead of just talking. Searching the web, running code, hitting an API, editing a file. Each one is a single action it takes to move the task forward.

The result of one tool call feeds into the next. The agent researches a topic, reads what came back, then uses that to build the PowerPoint. It keeps going around that loop, making tool calls, until the task is done.

Give an agent more tools and you give it more things it can actually do. A Chat model can only tell you how to run a Meta ad. An agent with the right tool calls can go and run it. That gap between telling you and doing it is the whole reason agents feel different to use.