Writing your company's voice so an AI can actually follow it.
"Friendly but professional" means nothing to a model. How to write a voice guide that works, and how to notice when the output drifts.
Every company's brand guide says something like "friendly, confident and professional". Hand that to an AI and you get the same bland, slightly breathless copy everyone else gets. Adjectives don't carry a voice. Examples do.
If AI is going to write your emails, pages and posts, your voice has to be written down in a way it can actually follow. Here's what works.
Replace adjectives with pairs
For each quality you want, write a pair: one sentence that sounds like you, and one that doesn't. "Plain" becomes: we write "you can cancel any time", not "we offer industry-leading flexibility across all our plans". The model learns far more from the contrast than from the word.
Five or six pairs covering your most common situations (a welcome email, a price, an apology, a product description) do more than a page of description.
Write down the phrases you never use
Every brand has words that make it wince. "Revolutionary", "seamless", "unlock", "leverage", "we're excited to announce". Write the list down. It's the fastest way to stop AI copy sounding like every other AI copy, because these are exactly the phrases models reach for by default.
Separate facts from voice
Voice is how you say things. Facts are what you say: your prices, what the product actually does, who your customers are, what you've promised. Keep them separate, and treat the facts as the stricter of the two.
AI is much more likely to get a fact subtly wrong than to get the tone wrong, and a wrong fact is the more expensive mistake. A pleasant email quoting last year's price is worse than an awkward email quoting the right one.
Keep it in one place
The fastest way to get an inconsistent brand is to paste a slightly different version of your voice guide into every prompt. Keep one source that every piece of work reads from, and change it there.
When you do change it, it helps to know what used the old version. If you update your pricing, the proposal written last week with the old price needs looking at. That's much easier if each piece of work records which version of your facts and voice it was made with.
Notice drift
Even with a good guide, output drifts. It starts using a phrase you hate, gets more formal over time, or starts inventing product claims. A few habits catch it early:
- Read a sample of finished work every week, not only the pieces that were flagged.
- When you fix something, add the fix to the guide as a new do-and-don't pair, so it doesn't come back.
- Watch for confident claims about the product that aren't in your facts. That's invention, not voice.
- Let the guide change on purpose. A voice that evolves deliberately is healthy. One that drifts by accident isn't.
A one-page template
Who we're talking to: one or two sentences.
Sounds like us / doesn't: five or six example pairs.
Never say: the banned phrase list.
Facts we never get wrong: prices, promises, what the product does and doesn't do.
When unsure: what to do, usually "ask, don't invent".
It fits on one page, an AI can follow it, and a new human hire can too.