Just prompt the AI to keep README concise and to the point, and to remove any implementation details that don't belong in README-style documents. I regularly run such debloating/decluttering prompts on my docs.
Give them 2 positive examples. A list of things to do, a list of things not to do and you have them giving you the exact output you want.
"Write a readme make no misteaks" is not deft usage.