The minimum structure
Define the recipient, objective, available context, tone, and next step. If a fact is missing, ask the model to flag it instead of making it up.
Base prompt
"Write a message for [person or group]. The objective is [objective]. Use only these facts: [facts]. Tone: [tone]. Maximum length: [length]. End with [next step]. Flag any missing information."
Review
Remove sentences that could be sent to anyone. Check names, numbers, and links. Read the message aloud before using it.