The blog is about writing an agent when you dont already have an agent, but only a plain LLM. It stitches the minimal pieces together. Agents dont need lots of supporting infra, so it is good to keep the code concise. Not a wow moment for sure, though some people think that agents and harnesses are complicated.
Right but given that the agent only outputs text, and agents are perfectly happy writing python, the supposed benefit of Lisp is completely irrelevant here.