Agents are nothing more than the core chat model with a system prompt, and wrapper that parses responses and executes actions and puts the result into the prompt, and a system instruction that lets the model know what it can do.

Nothing is really that advanced yet with agents themselves - no real reasoning going on.

That being said, you can build your own agents fairly straightforward. The key is designing the wrapper and the system instructions. For example, you can have a guided chat on where it builds of the functionality of looking at your calendar, google location history, babysitter booking, and integrate all of that into automatic actions.