What Is a PRD? How to Write One for an AI Tool

A product requirements document, or PRD, is a written note of what you are making, the limits you are working within, and how it should behave. For a small project it fits on one page. Its job is to remove guesswork and make "done" easy to check.

What goes in a one-page PRD

  • The person it is for.
  • Their problem.
  • The first task your version will help with.
  • What you will not build (non-goals).
  • Your assumptions, including how sensitive the information is.
  • A few things you can check to know it works.

Describe behavior, not technology

Keep what the product must do separate from ideas about how to build it. "Someone can't open another user's document" is a requirement. "Add this function" is an implementation detail. Checks that merely repeat how it was built don't test anything.

A small example

Suppose you want a local inquiry form. Your brief might say it must reject blank fields, identify an invalid email without clearing the message, work by keyboard, and state that no message was actually sent. Email delivery, accounts, and stored data are non-goals. Those few lines tell you what to build and what to check.

How to use it with an AI tool

  1. Paste the brief and ask the AI to restate it in its own words, so you can catch misunderstandings.
  2. Ask only the questions that block a useful or safe next step.
  3. When the AI builds something, compare it with each check in your brief.
  4. If it adds extra features, update the brief first, or remove them.

Common mistakes

  • Listing technologies without describing what people will do.
  • Leaving assumptions about private data unspoken.
  • Writing such a long document that it delays a small experiment.
  • Letting the AI quietly add features while claiming to follow the brief.

As your project grows

Add who is allowed to do what, what happens when something goes wrong, which devices it must work on, who keeps it running, and what must be true before launch. Keep a change log when new evidence changes the plan.

Go deeper with the free lessons

Start the Foundation. Last updated 2026-10-04.