AI tools write in an average voice unless you teach them yours. A brand voice guide built for AI is short, concrete and testable.
What a usable AI voice guide contains
- 3–5 voice traits with examples ("warm: we say you and we, never users").
- Words we use / never use — concrete lists, not adjectives.
- Claims rules: what needs proof, what is never said (for example "guaranteed", "#1" without a source, health claims).
- Reading level and format: sentence length, exclamation marks, emoji, capitalisation.
- Good and bad examples for each channel.
- An instruction block to paste into AI tools' system prompts or brand settings.
Values as rules, not just style
Brand rules for AI can also express what the brand stands for. In April 2024, for the 20th anniversary of its Campaign for Real Beauty, Dove committed to never use AI to create or distort women's images in its advertising, and published Real Beauty Prompt Guidelines to help people create more representative images with generative AI tools. That is a brand voice decision about what AI may depict, not only how copy sounds.
Make it checkable
Rules that can be checked automatically are the ones that get followed at scale:
- banned words and phrases,
- required disclosures,
- superlative and claim patterns,
- reading level and length,
- exclamation density.
Automated checks catch the obvious problems; humans judge tone, truth and taste.
Keep it alive
Review the guide every quarter with examples of AI output that went wrong and right. Add the fixes as rules. Share it with agencies and freelancers — they use AI too.