A brief is not a shopping list of deliverables. It is a shared definition of the problem, the stakes, and the conditions that will make an answer useful.
Describe the change
Start with what should be different after the work exists. Maybe a sales conversation becomes easier. Maybe a new audience understands the offer. Maybe the team can publish without asking a developer for help.
That change gives the project direction without prescribing its shape.
Name the constraints honestly
Timing, budget, internal politics, technical limits, legal review, and content capacity all affect the answer. Hiding them does not create more creative freedom; it creates rework.
Useful constraints let the team spend imagination in the places where it can survive contact with reality.
Keep one door open
The brief should be specific enough to align people and open enough for discovery to matter. If every page, feature, and line of copy is already decided, the creative team has been asked to decorate a conclusion.