Usually I just put something like "Prefer DRY code". I like to keep my AGENTS.md DRY too :)

also add "no hallucinations" and "make it works this time pretty please" while also say Claude will go to jail if does not do it right should work all the time (so like 60%)

There are of course limits to what prompting can do, but it does steer the models.

In TFA they found that prompting mitigates over-editing up to about 10 percentage points.

Similar to the observation (by simonw) that they respond reasonably to "TDD: Red => Green"

I've used that ever since. Works most of the time, but other stuff is often failing and I've learned to become distrustful of an agent very quickly. One mistake where I point it out and the agent corrects itself is fine if it keeps working well after. A second mistake when it's trying to fix the first one or an inability to understand or a claim that it fixed it but it didn't is instant termination (after dumping context for the next agent).