Why should a PRD be created before software development begins?

Why should a PRD be created before software development begins?

An early PRD gives implementation a clear purpose. Without shared requirements, different contributors may build reasonable solutions to different problems. AI assistants can increase the speed of that divergence because they can generate substantial code from assumptions that nobody has explicitly reviewed.

Agree on the outcome before investing heavily

For a wedding app, one person may imagine a guest-invitation tool while another expects a complete planner with tasks, budgets, and vendor management. Writing the initial scope makes that disagreement visible.

The PRD should identify intended users, priority workflows, important exclusions, and success criteria. These details help the team decide what to build first and what can wait.

A short, specific document can be more useful than a long description full of unresolved choices.

Expose dependencies and difficult decisions

Feature descriptions reveal questions that influence design and engineering. Task assignment needs a definition of collaborators. RSVPs need rules about guests, invitations, and multiple events.

Resolving key questions before substantial coding can reduce avoidable rework. Remaining uncertainties should be documented, with an owner or a planned experiment to investigate them.

A bounded prototype may still be appropriate when it helps answer a question the team cannot resolve through discussion alone.

Provide a basis for implementation and review

Once an initial scope is agreed, engineers and AI assistants can connect their work to explicit requirements. Designers can plan the needed states, and reviewers can check observable acceptance criteria.

The PRD remains changeable. New evidence may justify a different workflow or release scope, but the change should be recorded and reflected in related work. Preparing the document early supports shared understanding without requiring every detail to be permanently settled.