I have the best luck with RFC speak. “You MUST validate that the documentation validates existing code before implementation. You MAY update documentation to correct any mismatches.”

But I also use more casual style when investigating. “See what you think about the existing inheritance model, propose any improvements that will make it easier to maintain. I was thinking that creating a new base class for tree and flower to inherit from might make sense, but maybe that’s over complicating things”

(Expressing uncertainty seems to help avoid the model latching on to every idea with “you’re absolutely right!”)

RFC speak is a good way to put it.

Also, there's a big difference between giving general "always on" context (as in agents.md) for vibe coding - like "validate against existing code" etc - versus bouncing ideas in a chat session like your example, where you don't necessarily have a specific approach in mind and burning a few extra tokens for a one off query is no big deal.

Context isn't free (either literally or in terms of processing time) and there's definitely a balance to be found for a given task.