Business Center → Models lists the platform catalog. Owners and admins turn models on for the organisation. Builders see that list when they create an agent. A model that is off does not appear in the create-agent tray.
On Create agent, click a model to drop a preference into the composer. You can also name a default and a short list of recommended models in the chat. Recommended models feed automatic selection when a request does not name one.
An application may allow only some of the organisation’s models. The agent still cannot use a model the organisation has not enabled.