How to Write an AI Persona Brief, Starting With What It Must Never Do

Search for an AI persona template and you will find the same list every time: name, age, look, tone of voice, niche, a few brand values. Fill it in and the output is watchable for about two seconds, then something feels off and you cannot say what.

The briefs that hold up are built differently. They spend more lines on what the character must never do than on what she is, and each of those lines is blocking a specific way a generated person reads as fake.

Visual consistency is a solved and separate problem

Before the interesting part, clear this one out of the way. Keeping the same face across clips is a real problem with a known answer: anchor to a fixed reference image instead of re-describing the face in words each time. We covered that in keeping the same AI character across every video, and most of the character-sheet advice online is about this.

It is necessary and it is not enough. A perfectly locked face can still deliver a performance nobody believes, which is the failure mode we picked apart in why AI UGC ads look fake. What follows is the other half.

What a full brief actually contains

Seven sections, roughly in this order:

1. Positioning: who she is, who she is for, and one line on what she is not
2. Voice and speech habits: accent, pitch, pace, how sentences end, opening lines she reuses
3. The world: family, job, where she lives, who is around her
4. Scenes: the specific rooms she films in, down to what is on the counter, where the camera sits, what the light is like
5. Expressions and micro-expressions: not "friendly", but the actual sequence her face runs through
6. Wardrobe: by occasion, not in general
7. Habits: the small repeated behaviors that anchor her across videos

Most templates cover 1 and 2 and stop. Sections 3 to 7 are where a description turns into a person.

The negative constraints are the load-bearing part

Here is the pattern that shows up once you read enough working briefs. Look at what each line prevents:

The constraint	The failure it blocks
The partner is mentioned constantly but never appears on camera	The plastic look of a perfect couple performing for a lens
Her religion or background is context only, never announced	The persona flattening into a single label
Nine recurring phrases are listed, with "do not use them in every sentence"	A verbal tic where there should be a voice
"Not always the same controlled smile; the big laugh needs a bit of loss of control"	Expression that reads as a template
The counter always has clutter on it, "never empty like a showroom"	A set that looks like an advertisement
When the cooking goes wrong, "the mistake becomes content, no irritation"	Perfectionism, which is the fastest tell of all

Every one of those is a rule about not polishing something. That is the underlying principle, and it generalizes well beyond video: the thing that makes output read as machine-made is usually that it is too finished. Polish is the tell.

Which means a brief written only in positive terms is systematically biased toward fake, because positive description naturally reaches for the ideal version of everything. You have to spend lines pulling it back.

Expressions are sequences, not adjectives

"Natural" is not an instruction. The briefs that work write the actual beats.

A tasting reaction, for example, is not "she likes it". It is: look at the food, take a bite, a short thoughtful frown while chewing, eyes widen, small nod, mouth turns up, then the line. Seven beats, in order, with a note that it should not be an exaggerated eyes-closed reaction every time.

The same treatment goes to being interrupted by a child, to a recommendation, to the moment something goes wrong. Each gets a sequence. This is the difference between directing a performance and hoping for one.

Consistency anchors beat the face

The section that surprises people is the shortest one: a handful of small repeated behaviors.

Always gesturing with the same hand. A drink that always sits in the same place on the counter. A fixed line the dog gets when it comes near the food. A specific phrase when a product turns out well.

These matter because of how recognition actually works on a feed. The second time someone scrolls past you is the encounter that decides whether you exist to them. A face seen once is weak recognition. A habit seen three times is strong, and it survives a different outfit, a different room and a different topic.

Design the buyer first, then the person

One structural point that changes everything upstream of the brief.

The instinct is to build an appealing character and then find products for her. The stronger order is the reverse: start from the buyer segment you want, including their age, what they browse, what they actually buy, and then design a persona that segment already follows. The character becomes a consequence of the audience rather than a hopeful guess at one.

This is also what makes a persona replaceable without losing the account. If the segment turns out wrong, you can rewrite the person while keeping the account, its history and its face. The account is the asset. The persona is software running on it. If you are running more than one, the ordering matters even more: see how a persona matrix is actually run.

A worked example, invented for this post

To show the shape without pointing at anyone's live account, here is a made-up persona sketched to the structure above.

Positioning. 31, runs a small ceramics studio out of a converted garage, sells at weekend markets. For people who want to make things but think their space is too small. She is not a professional artist and never claims to be.

Voice. Slightly flat, dry, ends sentences early. Says "anyway" a lot. Opens with what went wrong, not with a greeting.

World. Partner works nights, so the studio is quiet in the evening. A neighbor keeps borrowing her clamps and never returns them, which is a running joke.

Scene. Garage: one wall of shelves with unglazed pieces, a kiln in the corner, a radio that is always on. Camera on the workbench, slightly low. Dust on everything, because a clean pottery studio is a lie.

Expressions. When a piece cracks: half a second of stillness, look at camera, small exhale, then keep going.

Habits. Wipes hands on the same apron spot. Puts the mug down on the left. When something works: "okay, that one's staying."

Never. Never a finished, styled shot of the workspace. Never calls anything "beautiful". Never hides a failed piece.

That last block took four lines and does more work than the four hundred words above it.

The short version

If you are writing a brief today, add three things most templates leave out:

1. A "never" list, with each line tied to a failure it prevents. Aim for at least six.
2. Sequences for two or three recurring reactions, written as ordered beats.
3. Three consistency anchors, small enough that they survive any topic.

Then check the order you built it in. If you designed the person before you decided who you were talking to, that is worth redoing before anything else.

When the brief is right, producing against it is the easy part. You can build a character and run it across videos and spend your attention where it belongs, which is on the brief.