The goal of a PRD is clarity. Not 10,000 words.

So whether you're writing it or generating it with AI, make sure your team can actually read and comprehend the purpose of what you're building in 10 minutes.

Or there will be a lot of "claude: give me the TL;DR for this", which at that point you're writing for agents and not people, then by all means, 20+ pages it is.