The task brief:
writing for an agent

In a conversation with AI you can refine the brief as you go. Not with delegation: the agent will work alone for 20 minutes with nobody to ask. Everything you don't say up front, it will guess — and possibly differently than you'd like.

That's why the four-part brief applies even more strictly with Codex:

With a task brief it also pays to specify the output structure ("split the code into three files") and what the agent must not do ("leave the existing logs untouched"). Less guessing, a more precise hit.

Exercise: write a task brief

Imagine you want an hourly rate calculator for freelancers: they enter costs, desired pay, vacation days and billable time — and see what they should charge. Write the brief for Codex and click Evaluate.

The checker is a simple aid — it checks the structure of your brief, not the quality of your idea. But if it flags something, the agent will have to guess it.

How the app grew out of it

This is a real run — Codex received the model brief above and built a finished app from it on a single brief, without a single correction. Including its own choice of calculation model.

Try the result

The app from the replay is real and exactly as the agent delivered it — including the design it picked itself.

Summary

• The agent doesn't ask while working — everything important goes in the brief.
• WHAT · WHY · HOW · WHEN it's done + output structure + what not to touch.
• A good brief = done on the first try. That's exactly what the replay shows.