Most brand voice documents are three adjectives on a slide. "Friendly, professional, innovative."
Hand that to a freelancer and you'll get back copy that's nothing like you, then spend two rounds correcting it towards a target you never actually described. The adjectives weren't wrong — they were unfalsifiable. Almost no brand describes itself as unfriendly or unprofessional, which means the words carry no information.
A voice document is useful in proportion to how much it constrains.
Adjectives don't transfer
"Direct" means blunt to one writer and concise to another. "Playful" produces puns from one person and warmth from another. "Professional" is the emptiest word in the set — it means "don't embarrass us", which everyone already knew.
The fix isn't better adjectives. It's replacing the abstraction with examples and rules.
The six parts
1 · Tone, as a small set of adjectives
Keep them, but treat them as a label rather than the substance. Three or four, and at least one of them should be surprising — a word a competitor wouldn't also claim. If all four could sit on any brand in your category, you haven't said anything.
2 · Who you're talking to
One sentence naming the reader specifically. "First-time founders building in public" is a voice instruction; "our customers" is not.
Voice is largely a function of audience. A writer who knows exactly who they're addressing gets the register right without being told.
3 · Do
Concrete, checkable rules. One per line.
- Lead with the payoff, not the setup
- Second person, present tense
- Short sentences, one idea each
- Name the specific thing — "a 90-second brand film" not "video content"
The test for each: could someone check whether a paragraph obeys it? "Be authentic" fails. "Never open with a rhetorical question" passes.
4 · Don't
The higher-value list, and the one people underwrite.
Prohibitions are unambiguous in a way that positive guidance isn't. Include the specific banned words — the hype vocabulary, the phrases your industry overuses, the constructions that make you wince.
Be petty here. Petty is useful. "Never write 'in today's fast-paced world'" is more actionable than a paragraph about being modern.
5 · Signature phrases
The actual words and constructions you use. Not a tagline — the recurring turns of phrase that make your writing recognizable.
Most brands have four or five and have never written them down. Find them by reading your best-performing copy and noticing what repeats.
6 · Before-and-after pairs
The most valuable section, and the most commonly missing.
Take real sentences and show the rewrite. Five or six pairs teach more than two pages of principles, because they demonstrate the transformation rather than describing the destination.
Two things worth adding
Register range. Voice isn't one setting. How you sound in an error message differs from a launch announcement differs from a comment reply. Name two or three contexts and note what shifts — usually formality and length, rarely the underlying personality.
What you never say. Claims you won't make, comparisons you won't draw, topics you stay out of. This is a voice constraint as much as a legal one, and it's the thing a new writer is most likely to get wrong on their first attempt because nobody thought to mention it.
Find your voice by reading, not by workshopping
The common failure is deriving voice from aspiration in a meeting. You end up documenting how the brand would like to sound, which nothing you've published actually does.
Do it the other way round:
- Collect twenty pieces of your copy — the ones that worked and felt right.
- Read them together and mark what recurs. Sentence length, how you open, whether you use questions, how much hedging, where humour sits.
- Write down what you observe, not what you'd prefer.
- Then decide, deliberately, what you want to change — and mark those as changes rather than descriptions.
That last step matters. A document that mixes "this is how we sound" with "this is how we'd like to sound" produces confusion for anyone using it, because they can't tell which lines describe reality.
Test it before you rely on it
Give the document — and nothing else — to someone who's never written for you. Ask for three sentences on a topic you'd normally cover.
If it comes back wrong, the document is wrong, not the writer. Look at which way it's wrong and add the rule that would have prevented it. Two or three cycles of this produces a genuinely useful document, and there is no substitute for the test.
Where Acumin fits
Brand Voice captures exactly this shape — tone, audience, do and don't lists, signature phrases, sign-off — and it's infer-then-refine: it proposes a starting profile from what you've published, and you correct it. Starting from a draft you disagree with is considerably faster than starting from an empty page, because disagreement is specific.
The saved profile then guides tone everywhere Acumin writes — ad copy, hooks, brief language, drafted comment replies. It shapes how things are written and never invents facts or numbers, which is the same doctrine that runs through the rest of the product.
Two honest limits. It can only infer from what you give it, so a thin input produces a generic profile. And a voice profile makes drafts sound like you — it doesn't make them right. Someone still reads before anything goes out.
How to use this today
Take your five best pieces of copy and one bad one. Read them in a row.
Write the six before-and-after pairs that the bad one suggests. That's a more useful voice document than most brands have, and it took an hour.
Related: Building a brand library is the same reusability idea for the physical side of production. Replying in brand voice, at scale, honestly is where a voice document earns its keep daily.