Upgrade a weak prompt into a strong one

Prompt

Turn this weak prompt into a strong one I can paste into ChatGPT or Claude.
Keep my intent. Add: goal, audience, inputs, constraints, output shape, and what to do when info is missing. Use #placeholders# for anything I still need to fill. Return only the upgraded prompt, then 3 fill-in hints.
Weak prompt:
#weakprompt#