Once an agent is connected, most of what you would do in the app you can ask for in a sentence instead. It works under your account: your usage, your plan limits, and only the accounts where you are an owner or admin. Creating and publishing need an active plan. Without one, for example with only usage packs or while your plan is paused, an agent can read your account but not render or publish for you.
It can set up a Series and change it later, duplicate one, pause it, resume it, or archive it. Archiving is final: the Series never posts again and there is no way to bring it back. It can render a one-off video or the next post of a Series, re-roll the music or the visuals or a single track, and make the same edits you would in Studio: lock a layer, change a video's length, rename a track. When a video is ready it can publish to YouTube now or on a schedule, with the title, description and tags set. The demo video from onboarding is shared footage rather than one of your renders, so an agent can read it but not edit, re-roll or publish it.
It can read your channel and per-video analytics and pull out your best performers. Those numbers come from a stored copy, so when they look stale you can ask it to refresh them. It can also search your Library and reuse a saved track, image or video in a new render, check the mission board and collect the extra usage you have earned, and export a snapshot of your account data.
Renders and re-rolls use your usage exactly as they would in the app: your monthly usage first, then your usage packs if Extra usage is on. Nothing else an agent does uses any. Ask whether a render fits and it tells you before it starts one. If the render needs more than you have left, it is refused before anything runs, and the agent tells you there isn't enough usage left.
There is also a cap on how many renders an agent can start in an hour, and Rate limits for connected agents has the numbers. To see what yours has been doing, the Recent activity table at Settings → Authorized agents keeps a rolling 30 days.