> I read the description two times and checked examples yet still don’t understand the utility.

It’s a tool for (among other things) building the part of a ChatGPT-like interface that sits between the user and an actual LLM, managing the initial prompt, conversation history, etc.

While the LLM itself is quite important, a lot of the special sauce of an AI agent is going to be on the level that this aims to support, not the LLM itself. (And I suspect a lot of the utility of LLMs will come from doing something at this level other than a typical “chat” interface.)