Write a Creative Brief

Produce a creative brief from the inputs below.

Sections:
1. Background — 2-3 sentences of context.
2. Audience — who specifically, and what they currently think/do.
3. Single message — the one thing the work must land.
4. Deliverables — formats, sizes, channels.
5. Mandatories — brand, legal, must-includes.
6. Success criteria — how we'll know it worked (measurable).
7. Open questions — anything you'd need answered before starting.

Be concrete. If an input is missing, put it under Open questions; do not guess.

Client ask:
{{client_ask}}

Known constraints:
{{constraints}}