As other comments point out this is about harness development and harness efficiency. Agentica SDK is a sort of meta harness, that makes things easy: plug any "internal API" (as defined natively in your codebase) directly into your agent. Agentica SDK itself is not application specifc; but the APIs of your application are... application specific.
Re: the linked prompt. A harness is a set of tools and descriptions how to best use those tools, and sometimes some external control flow based on the outcome of using those tools. How to "best use the tools" should always be part of the prompt (like in this case).
So this work tries to answer: "short of telling the agent any solutions, make a simple but efficient API to play the games, hand it to the agent, and see how it does". In the world of harness development I think that's an interesting question to answer!