Translate your voice into observable rules
Words such as friendly, professional or bold are too broad on their own. Describe sentence length, vocabulary, level of formality, use of humor and the way you explain difficult ideas.
Add boundaries as well as preferences. List phrases, claims and habits that should never appear. A useful voice brief tells the model what to avoid, not only what to imitate.
Provide examples with explanations
Give two or three short examples that genuinely sound like the brand. Explain why they work: direct opening, concrete language, calm authority or a practical ending.
Include one negative example and identify the problem. This contrast helps the model distinguish your voice from generic promotional writing.
Use a repeatable review checklist
Check every draft for accuracy, specificity, rhythm and credibility. Replace generic claims with evidence or real experience, and remove phrases you would not say to a client.
Save the corrections that recur. They reveal missing voice rules and make the brief stronger for the next prompt.