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The prompt is the new creative brief
Writing for agents is a craft. The structure, constraints and taste signals that make a build land on the first pass.
Benjamin Stanley
AI Product Strategist
The creative brief did not disappear when agents arrived. It got shorter, faster to write, and much less forgiving of vagueness. A human designer will quietly fill the gaps in a bad brief using context you never gave them — they met you, they saw your office, they know what your competitors look like. An agent fills those gaps too, but from a different place: the statistical middle of everything it has seen. That is exactly where generic output comes from. A good prompt is not a longer prompt. It is a prompt that closes the gaps you care about and deliberately leaves open the ones you don't.
Three things a brief must carry
Everything useful in a design brief falls into one of three buckets, and most bad briefs are entirely made of the first.
Instructions are what to make. A homepage, three sections, a pricing table. Necessary, and the least valuable part — this is the bucket people overfill.
Constraints are what must be true. Readable on a phone in daylight. Loads under two seconds on 3G. Must work without the founder's photo, because she won't send one. Constraints do more work than instructions because they eliminate wrong answers rather than describing a right one.
Taste signals are how it should feel, and they are the hardest to write and the most decisive. Calm not corporate. Should feel like a tool, not a brochure. Nothing that looks like it was designed by a committee at a bank.
A bad prompt and a good one
Here is a real prompt, lightly anonymised, that produced four rejected rounds:
Every word is an instruction, and every one of them describes the average of the category. Modern, clean, professional, premium — these are words that eliminate nothing. Blue and white is the default palette of the exact market you are trying to stand out in. The section list is the section list of every landing page ever made.
The rewrite, from the same founder, three days later:
Shorter in instructions, far richer in constraints and taste. It produced an accepted layout on the second pass.
Negative space in a brief
The single highest-leverage sentence you can write is what to leave out.
"No testimonial section — we have two customers and both are under NDA" saves an entire round. Without it, the agent builds the section, you delete it, and the layout rebalances awkwardly around the gap. Worse, agents optimising for completeness treat an empty section as a problem to solve and will fill it with placeholder social proof, which is the fastest way to make a real product look fake.
What you write | What it prevents |
|---|---|
No testimonials yet | Placeholder quotes and fake logos |
One integration only | A logo row of one, or six invented ones |
No founder photo | An About section built around a headshot |
Copy will change | Layouts that break when text length shifts |
Pricing is not final | A pricing table treated as load-bearing |
Write the failure state
Ask yourself what would make you embarrassed to ship this, and write that sentence down. It is the most efficient taste signal in existence, because it defines a boundary instead of a target.
"I'd be embarrassed if it looked like every other SaaS page" rules out more design space in eleven words than a paragraph of positive description could. Positive descriptions point at a region and hope. Negative boundaries carve the space up.
The half-page rule
If your brief is longer than half a page, you are probably designing rather than briefing, and you'll get worse results than if you'd written less. Every additional instruction closes a door the agents might have walked through.
The brief that works is roughly this shape: two sentences on who this is for and in what state of mind, two or three hard constraints, one taste signal, one thing to leave out, and one sentence describing what failure looks like. Seven sentences. Five minutes.
Then stop, and let it disagree with you. The disagreement is the part you're actually paying for.