A brief is not a container for everything you know about the product. It is a decision about what this particular piece of work has to do, written down so that everyone stops relitigating it.

Most briefs fail because they refuse to choose. Five objectives, four audiences, three tones of voice. The writer then picks for you, badly, at eleven at night.

Write one sentence about who this is for, one about what they currently believe, and one about what you want them to believe afterwards. If you cannot fill those three lines, the problem is upstream of the brief.