PRD mistakes are not random — they follow predictable patterns. 68% of engineering re-requests trace back to missing or vague acceptance criteria (Scriptonia, 2026). These 10 mistakes cover the full spectrum of how PRDs fail — and each has a specific fix.
"A PM who writes bad PRDs isn't bad at product management. They're bad at PRD writing — which is a separate skill. The good news: it's entirely learnable, and the feedback loop is short."
— Ryan C., Engineering Director at a mid-size SaaS company
The 10 mistakes and their fixes
1. Vague acceptance criteria
Mistake: "The feature should work as expected."
Fix: Given/When/Then format. "Given a user with Export permission, When they click Export CSV with a 30-day range, Then a CSV downloads with these exact columns."
2. Missing edge cases
Mistake: Writing only the happy path.
Fix: For every user story, ask: what happens when the user doesn't have permission? When the data is empty? When the action times out? Document at least 3 edge cases per feature.
3. Architecture prescriptions in requirements
Mistake: "The system should use PostgreSQL and Redis for caching."
Fix: "The system should return search results in under 500ms." Specify the requirement; let engineering own the implementation.
4. Unmeasurable success metrics
Mistake: "Improve user engagement."
Fix: "Increase the % of users who export data at least once per month from 8% to 25% by Q3 end."
5. No out-of-scope list
Mistake: Listing what's in scope without explicitly stating what's out.
Fix: Every PRD must have an explicit out-of-scope list. The out-of-scope list is what prevents scope creep.
6. Hidden open questions
Mistake: Burying unresolved decisions in paragraph prose.
Fix: Explicit Open Questions section. Each entry: the question, the owner, and the resolution deadline.
7. Vague personas
Mistake: "Users want to export data."
Fix: "Admin users at enterprise accounts (50+ seats) who need to share usage reports with non-product stakeholders." Specificity drives better edge case coverage.
8. Missing dependency status
Mistake: Listing dependencies without ownership or status.
Fix: Dependency table: external system | owner | current status | blocking or non-blocking.
9. Post-launch metrics never reviewed
Mistake: Defining success metrics in the PRD, never reviewing them.
Fix: Book 30-day and 90-day metric review meetings before sprint starts. Put the dates in the PRD.
10. Scope changes without documentation
Mistake: Mid-sprint scope changes communicated verbally.
Fix: Every scope change requires a PRD update with a version note: what changed, why, and when.