Guide · Updated 2026-10-08

How to Write a Clear Brief or AI Prompt

The parts of a good project brief or AI instruction, how to replace vague words with measurable ones, how to avoid conflicting rules and how to check your work.

Whether you are hiring a developer, briefing an agency or giving instructions to an AI assistant, the quality of what you get back depends on the clarity of what you ask for. The same few habits improve all of them: say what you want and why, make it measurable, and remove anything that contradicts itself.

The parts of a good brief

Part	What to write	Example
Background	The problem and who has it	Our clinic takes bookings by phone, so calls are missed and appointments are double-booked.
Users	Who will use the result	Patients and reception staff
Goals and measures	What success looks like, with numbers	Cut phone bookings by 60% within 3 months
Must-haves	The few things that must exist	Patients can see free slots and book online
Nice-to-haves	What can wait	SMS reminders
Constraints	Budget, deadline, rules, tools	£8,000, launch by 1 March, UK GDPR
Acceptance criteria	How you will decide each item is done	A booking cannot overlap another for the same practitioner
Open questions	What you do not know yet	Do we need online payment?

The Brief Builder asks for these parts and writes a Markdown brief, with a clarity check on vague wording, missing numbers and missing deadlines.

Replace vague words with something you can test

Words such as fast, easy, modern, robust, user-friendly and appropriate mean different things to different people. Each one hides a decision. Replace them with a number, an example or a pass/fail test.

Vague	Clear
A fast website	Pages load in under 2 seconds on a mid-range phone over 4G
Easy to use	A new patient can book an appointment in under 3 minutes without help
Secure	Passwords are hashed, access requires login and data is stored in the UK
Looks professional	Uses our brand colours and fonts, and matches the layout in the attached mock-up
Respond appropriately	Reply politely, in under 120 words, and offer a link to the relevant help page

Avoid rules that contradict each other

Long instruction lists grow by accretion, and they quietly start to disagree. A typical example is a prompt that says "Always keep answers short" in one place and "Always write detailed, thorough explanations" in another. A human reader will ask which one wins. An AI model has to guess, and may guess differently each time. When you spot a conflict, either remove one rule, or add a condition: "Keep answers under 100 words, unless the user asks for a detailed explanation".

Other things to check: the same rule repeated in different words, capital letters used to shout ("NEVER"), rules that are very long and do several things at once, and missing basics such as an output format, what to do when unsure, and one or two examples. The AI Instruction and Prompt Checker scans your text for these, using text rules rather than AI, so it can flag likely problems for you to review.

Give examples

One or two examples of the output you want, even rough ones, remove more ambiguity than a paragraph of description. Show a good example and, if useful, a bad one with a note about what is wrong with it.

State what to do when unsure

Say whether the assistant or contractor should ask a question, make a sensible assumption and flag it, or stop. Without that, people and models guess, and sometimes do something costly.

Write testable acceptance criteria

For each must-have, write a sentence that someone else could check as pass or fail: "A patient receives a confirmation email within 1 minute of booking" rather than "Patients get notified". If you cannot tell whether a criterion has been met, it needs rewriting.

Test the brief before you send it

Read it as someone who knows nothing about your business. What would they ask?
Run it through the checkers for vague wording and conflicts.
Ask one person to explain it back to you in their own words.
For AI instructions, try three or four real examples, including awkward ones, and fix the rules that fail.

After the meeting: capture what was agreed

Briefs change in conversations. Afterwards, list who agreed to do what and by when. The Meeting Transcript to Action List pulls tasks, owners and deadlines from a transcript, with the passage each came from so you can verify it, though you should check its list against the original.

Frequently asked questions

How long should a brief be? As short as it can be while answering the questions a stranger would ask. One to two pages is usual for a small project.

Does a good prompt need to be long? No. Clear, specific and consistent instructions usually beat long, repetitive ones. Every line should say something the reader would otherwise get wrong.

The examples are illustrations of the method. Adapt them to your own project.