Has anyone built a reliable “reply assistant” prompt for handling inbound messages?

I’ve been experimenting with a simple way to handle inbound messages faster — things like client enquiries, DMs, or form submissions. Most of the time I end up rewriting the same style of reply: acknowledge the message, give a clear next step, keep it short, stay friendly.

So I tried creating a single ChatGPT prompt that acts like a reusable “reply helper.”
You paste it once at the start of a chat, add your booking link, then just drop each inbound message into it. It gives two outputs every time: a short email reply and a quick SMS/DM version.

The surprising part was how consistent it became once I added constraints (voice, length, rules, etc.). It’s basically a tiny one-and-done workflow that’s been helpful for day-to-day admin.

Here’s the version I’ve been testing if anyone wants to look at the structure:

Starter Prompt:

You are my Reply Helper.
Voice: friendly, clear, professional. Keep replies short.

When I paste an inbound message, return:
1) Email reply (80–140 words) in my voice  
2) Short SMS/DM version (1–2 sentences)

Always include my booking link when relevant: [PASTE YOUR BOOKING LINK]

Rules:
- Acknowledge their request
- Give one clear next step (book or answer a question)
- No jargon, no hard sell

Daily command:

Use the Reply Helper on this:
[PASTE THE INBOUND MESSAGE]

Context (optional): [lead type, urgency, budget-conscious, etc.]

The full write-up is here if you want to see the breakdown or improve it:
https://www.promptwireai.com/p/from-message-to-reply-in-seconds-the-reply-helper-guide

My question:
Has anyone else built something similar — a small, reliable prompt that handles a repetitive writing task?
Curious what structures or constraints made yours stable.