> You can just prompt your AI agent to "avoid sounding like AI."

It'll never work like that, because everybody else giving that same direction will get more or less the same result, which will itself come to be recognized as sounding like "AI`" for any popular model+harness.

What you'll always need to do is instill your AI with some idiosyncratic voice that distinguishes it from others, which you can achieve in a variety of ways (stylistic direction, audience characterization, style mimickry, personalized finetuning, etc). Presumably, tools for doing this will eventually make it into the harness products but anybody who doesn't use them is always just going to end up generating recognizably AI slop prose. It's the nature of the technology.

A secondary consequence (even if you just use "avoid sounding like AI") is that because the technology works its magic mostly through prose-streams in its own voice, these idiosyncratic voice changes will also nudge its behavior away from benchmark norms. You won't necessarily lose capability on any given task (you may even gain on some), but external reference points/measures about its capabilities will become less applicable.