You do not need a perfect document to start a conversation. A useful brief gives your creative partner enough context to understand the business problem and ask the right questions.
Start with the outcome
Describe what you want to change, who the work is for, and what a useful result would look like. Separate the business goal from the deliverables you are considering.
Share the context and constraints
Include your audience, current brand or website, essential features, ideal timeline and any budget range you are comfortable sharing. If something is flexible, say so.
Keep your files in one place
Put relevant documents, brand assets and references into a Google Drive folder. Share a viewer link in your project brief. For confidential material, use restricted access and invite the agency rather than making the folder public.
A good reference explains what you like and why. It does not need to be a design you want to copy.
Agree the next step
After reviewing the brief, your agency should clarify the scope, responsibilities, milestones, review process and fees before production starts. Keep the final decisions in the project conversation so everyone can refer back to them.