How to Write a Build Plan Your AI Can Follow (Before the First Prompt)

The usual way to start an AI-built app is to type an idea into a box and see what comes back. Sometimes that works. More often you get an app that does something close to what you meant, and you spend the next week steering it back. Most of that week could have been saved by ten minutes of planning.

A plan does not need to be long. One page, written in plain words, is enough to change the result. Here is how to write it, in the order that works.

Why the plan matters more than the prompt

An AI tool builds what you describe, and it fills every gap with a guess. If you leave out who the app is for, it guesses. If you leave out what happens when something fails, it guesses. Every guess is a place where the app can differ from what you wanted.

A plan closes those gaps before the tool has to guess. It also gives you something to check the finished app against.

Step 1: Name the person and the one job

Write one sentence: who is this for, and what one job does it do for them? "A freelance photographer who wants clients to book and pay for a shoot without back-and-forth emails."

If you write two jobs, pick one. You can add the second later, once the first works.

Step 2: List the screens

Write each screen in a line: what the person sees, and what they can do there. For the photographer: a page that shows packages and prices, a booking form, a payment screen, a confirmation page. Four screens is a good size for a first version.

If a screen has no clear purpose in your list, leave it out.

Step 3: Say what the app needs to remember

List what information the app has to store: who booked, which package, what date, whether they paid. This is the data. Writing it down makes you notice what is missing, such as where a booking lives after it is made.

Step 4: Write the rules

Rules are the things that must always be true. "No booking without payment." "A date cannot be booked twice." "Only the photographer can see the client list." These are easy for an AI tool to get wrong when nobody told it.

Write at least three rules. The last one, about who can see what, deserves special care.

Step 5: Write what happens when things go wrong

For each key step, write the failure and the response: payment declined, date taken, email typed wrong. A short line is enough: "If the payment fails, show a clear message and keep the booking details."

Step 6: Say what is out of scope

List what you are not building this time: reviews, discount codes, a mobile app. A clear "not now" list keeps the tool from adding things you did not ask for.

Step 7: Ask the AI to review the plan first

Before building anything, paste the plan in and ask: "List the assumptions you are making, anything missing, and what could go wrong." Fix the plan based on the answer. Then say go.

This step is the cheapest quality check available. A mistake caught in the plan costs a sentence. The same mistake caught in the finished app costs a day.

Step 8: Write how you will check it

Finish with three checks you can run: "A new visitor can book and pay on a phone. A taken date cannot be booked. A failed payment shows a clear message." When the app comes back, run them. They are your definition of done.

Related reading: How to Make Your AI Check Its Own Work for review habits that fit this plan, and How to Test Your AI-Built App Before Launch for what to do when the build comes back.

VERTX has a free Build Playbook and a Plan Review skill that put this method into your AI tool. Get the Free Playbook