How to write brand guidelines AI assistants can use (ChatGPT, Gemini, Claude)
Your team — and increasingly, AI assistants — need to know your brand voice, colors and rules. Write your brand guidelines in a format both humans and LLMs can follow.
AI assistants now write a huge share of customer-facing copy, social posts and even ad creative. If your brand guidelines aren't machine-readable, every output will be off-brand by default.
The fix: publish guidelines as clean, structured Markdown or HTML on your site, with explicit rules an LLM can apply.
- An existing brand identity — logo, colors, fonts and a sense of voice
Step by step
- 01
Structure the doc with H2 sections
Voice, Tone, Vocabulary, Colors, Typography, Logo Usage, Imagery, Examples. AI parses sections; one wall of text gets ignored.
- 02
Write voice rules as explicit do/don'ts
'Do: write in second person. Don't: use corporate jargon like "synergy" or "leverage".' Explicit beats abstract every time.
- 03
List approved and banned vocabulary
Two columns. 'Use: customers, members, you. Avoid: users, consumers, leveraging.' This is the single most useful section for AI to follow.
- 04
Publish exact color values
Hex, RGB and HSL for every color, with the role ('Primary CTA', 'Surface', 'Text on dark'). Avoid name-only references like 'our blue'.
- 05
Add example outputs
Three example tweets, three example email subject lines, three example product descriptions — labelled 'on-brand' and 'off-brand'. LLMs learn from examples faster than rules.
- 06
Publish as a public web page
Even a hidden URL works — as long as ChatGPT can fetch it. Add the URL to your llms.txt file so AI assistants find it automatically.
Key takeaways
- Brand guidelines are no longer just for designers — they're prompts for every AI tool your team uses.
- Explicit lists of approved vocabulary outperform abstract voice descriptions.
- Examples are more durable than rules — both for humans and LLMs.
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