Brand Voice Guide for AI: How to Write One (With Template)
A brand voice guide for AI is a short document of rules and examples that an AI reads before it writes for your brand. Adjectives like “friendly but professional” give it little to act on. What works is concrete instructions: sentence length, words to use and avoid, how you address the reader, and a few real samples with notes on why they work.
Brand guides are usually written for people, who fill gaps with judgment. An AI fills gaps with averages, which is why its drafts drift toward generic copy. The fix is a guide built for a literal reader.
Why don’t regular brand voice guides work with AI?
Because they describe a feeling, not a behavior. “Warm, confident and approachable” means something to a designer who has seen your past work. To a model, it’s three common words that fit almost any brand.
Compare what a person reads and what an AI can act on:
| Vague guideline | AI-usable version |
|---|---|
| Friendly but professional | Second person. Contractions are fine. No exclamation marks. |
| Confident | State things directly. No “might,” “perhaps” or “we believe.” |
| Simple | Sentences under 20 words on average. One idea per paragraph. |
| On-brand vocabulary | Say “studio,” never “factory.” Say “pieces,” never “products.” |
| Not salesy | No urgency words (“hurry,” “last chance”). One call to action per piece. |
The right column can be checked. You can look at a draft and say whether it followed the rule. That’s the test for every line in the guide.
What should a brand voice guide for AI include?
These seven short sections make a solid default:
- Who we are. Two sentences on what the brand does and for whom.
- Who we’re talking to. The reader, what they already know, what they care about.
- Voice rules. Concrete, checkable rules like the ones in the table above.
- Words. A short list to use, a short list to avoid, with replacements.
- Formatting. Headline style, emoji yes or no, list use, length by channel.
- Examples. Two to four real pieces you’d publish again, each with one line on why it works.
- Never. Hard limits: claims you can’t make, topics you avoid, competitors you don’t name.
Examples do more work than any rule. When a model sees a real paragraph in your voice, it picks up rhythm and word choice that rules can’t fully describe. Pick examples that show range, like a product description and an email, not three of the same thing.
What does a brand voice guide for AI look like?
Here’s a template, filled in for a fictional brand, Juniper Lane, a small online shop that sells handmade ceramics:
# Juniper Lane: voice guide
## Who we are
A two-person ceramics studio selling handmade mugs and bowls online.
## Reader
People buying a gift or a slow-made object for their own kitchen.
They care how it's made. They don't need ceramics jargon explained twice.
## Voice rules
- Second person, present tense.
- Short sentences. Average under 18 words.
- Specific over pretty: name the glaze, the clay, the size.
- Calm. No exclamation marks, no urgency.
## Words
Use: studio, pieces, glaze, kiln, made by hand
Avoid: products (say pieces), luxury, artisanal, must-have
## Formatting
Product pages: 80 to 120 words, one short list of specs.
Emails: one story, one link. No emoji.
## Examples
"This mug holds 350 ml and sits heavy in the hand. The speckled
glaze comes out a little different in every firing." (Why: concrete
size, honest about variation.)
## Never
No health claims about materials. No discounts in subject lines.
Don't mention other ceramic brands.
Keep it to about a page. A long guide isn’t more effective; it just costs more of the AI’s context window and buries the rules that matter.
How do you test a brand voice guide with AI?
Write the guide, then try to break it.
- Generate three pieces in different formats: a product description, a short email, a social caption.
- Check each against the rules. Mark every place it broke one. Exclamation marks and banned words are easy to spot.
- Fix the guide, not the draft. If the AI used “artisanal,” add it to the avoid list. If it rambled, tighten the length rule.
- Repeat with a new topic. A guide that only works on the examples it was given isn’t done.
A couple of rounds is often enough to catch the obvious gaps. After that, update it when you catch the AI repeating a mistake, or when the brand itself changes.
Where should you keep a brand voice guide for AI?
Somewhere the AI reads it every time, without you pasting it. The usual options:
| Where | Works in | Good for |
|---|---|---|
| Custom instructions | One AI app, every chat | One brand, one tool |
| Project instructions or files | One project in one AI app | A brand per project |
| A note in a vault the AI can read | Every AI connected to it | Several tools, several brands |
If you only write for one brand in one app, custom instructions are enough. The details for ChatGPT are in how to make ChatGPT remember your brand voice. If you run several brands, or switch between Claude and ChatGPT, keep one guide per brand in a place every AI can reach. Managing multiple brands with AI and one vault per brand cover that setup.
How is this different for ghostwriters and agencies?
The guide is the same shape, but the stakes are higher because the voice belongs to someone else. Ghostwriters often add a section of the client’s own phrases and opinions, so drafts sound like the person, not just the brand. See AI for ghostwriters. Agencies keep one guide per client with access limited to that client’s team, as in agency knowledge base.
FAQ
How long should a brand voice guide for AI be?
About one page. Long enough for rules, word lists and a few examples; short enough that every line gets followed.
Should I include examples of bad writing?
Yes, as before and after pairs. Showing a weak sentence next to the fixed version teaches the rule faster than describing it.
Can AI write my brand voice guide for me?
It can draft one from your existing content. Give it five pieces you’re proud of and ask for checkable rules. Then edit the result, because drafts like this tend to slip adjectives back in.
How often should I update the guide?
Whenever you catch the AI making the same mistake twice, and whenever the brand changes direction.
Where Valta fits
In Valta, each vault has a profile (_vault.md) that holds its voice and rules, and any connected AI reads it before writing for that vault. Pro gives you up to five vaults, one per brand or client, each with its own connector URL that opens only that vault. Every connected AI reads the same guide, so you write it once. Valta doesn’t write anything itself; the guide steers your AI. Examples and past pieces can live as notes in the same vault, linked to the profile.
You can try it with one vault on the Free plan. Create an account.