The worst PRDs I've written were complete. Every field filled, every screen described, still useless, because they recorded decisions without recording why.
THE THREE QUESTIONS
A PRD earns its keep when a new engineer can answer, without asking: what problem is this for, what counts as done, and what did we decide not to do. On a zero-balance account we built for gig workers, that third question is what kept the backlog honest: writing down what we weren't building yet, and why, stopped old scope from quietly returning mid-sprint wearing a new name.
ACCEPTANCE CRITERIA ARE THE SPEC
If a line can't be tested, it's a preference, not a requirement. Writing criteria first exposes the parts of the problem still unresolved, which is exactly the part worth arguing about early, before a sprint starts, not during UAT.
KEEP THE CUTS VISIBLE
A short "not now" list saves more time than any diagram. It's the fastest way to show a stakeholder that no was a decision, not an oversight.