Start with the outcome
A useful brief explains the problem to solve and the result the client expects. Describe the current situation, the people affected and a practical measure of success. Keep confirmed facts separate from assumptions that still need approval.
Define the deliverables
List what the project will produce, not only the activities your team will perform. For each deliverable, record the expected format, the reviewer and the acceptance criteria. Write down exclusions as clearly as inclusions: this helps both sides recognize requests that change the scope.
Record dependencies and decisions
Ask which systems, assets, access permissions and client decisions the work depends on. Name the person responsible for each dependency and agree when it is needed. A delivery date is only useful when the assumptions behind it are visible.
Discuss schedule and budget
Separate a target launch date from a confirmed delivery commitment. Record the budget in an explicit currency code, and clarify whether figures include tax. A document currency is a commercial choice for that project; it need not match the currency used to pay for your software subscription.
Keep a reviewable record
In Mideo, you can collect requirements in a brief and use comments to resolve open questions. Review the completed answers before preparing a proposal. The purpose is not to fill every field with a guess, but to make the scope and remaining decisions understandable to the client and your team.