A brand voice isn't a list of adjectives. It's the handful of choices you'd make the same way every time: how you greet people, what you never say, how you end a post.
Answer five questions
- Who are you talking to? One real customer, described in a sentence.
- Three words for how you sound, and one word you never want to sound like.
- Words and phrases you always use, and ones you never do.
- How formal are you? Do you use emoji? Exclamation marks?
- What would you never claim, even if it's true?
Then show, don't describe
Pick three past posts that sound exactly right. Examples teach a writer, or Juper's Brand Brain, faster than any description.