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Guide

Customer email prompt template: from rough notes to a reply

An annoyed customer, a postponed installation and an open question about costs. With a good prompt, that becomes a draft reply you can check against your facts before it goes out.

Published October 6, 2026 • 4 min read

“Reply politely to this email” is a typical office prompt. The AI will write something polite, but it doesn’t know your new date or your goodwill policy. It fills those gaps with plausible sentences, and in a customer email that can turn into a promise nobody made.

This guide works through one example to show what belongs in the prompt. The company, the customer and the dates are invented.

In short

  • Give the AI the customer’s email and your internal facts as separate blocks.
  • Say outright what it must not promise, and have it mark any gaps.
  • Check the draft against the facts before you worry about the tone.

The situation

A heating company was due to install a heat pump on Thursday 12 November. According to the supplier, the outdoor unit won’t arrive until the week of 23 November. The customer writes:

Hello, I haven’t heard from you in three weeks. Are we still on for 12 November? Our old boiler is cutting out almost every day. And who is going to pay for the fan heaters I now have to buy? Kind regards, S. Bennett

What the site manager knows goes into the prompt under FACTS. Nobody has decided yet whether to refund the fan heaters.

The prompt

Copy the block and replace the details with your own, as long as your AI policy allows this kind of customer data in the tool you’re using.

You write for the customer service team of a heating company.
Draft a reply to the customer email below.

CUSTOMER EMAIL
"""
[paste email]
"""

FACTS (use only these)
- Installation postponed, earliest Wednesday 2 December.
- Reason: supplier says the outdoor unit arrives in the week
  of 23 November.
- We will confirm the exact day once the unit has arrived.
- We lend an electric heater free of charge, collection or
  delivery by arrangement.
- Contact: Mr Hayes, site manager, extension 23.

DO NOT PROMISE
- Payment of electricity costs or purchased fan heaters.
  No decision has been made on this.
- A fixed installation date.

TASK
- Answer every question the customer asks, including the one
  about costs.
- Apologise once for the lack of contact.
- Where information is missing, write [OPEN: ...] instead of
  filling it in.

FORMAT
Polite and factual, 130 words at most, with a subject line.

The block separates the email, the facts and the limits, so the AI can tell what the customer wrote from what you can commit to. Microsoft also advises naming the goal, context, source and expectations in a prompt. The [OPEN] line follows advice from the Anthropic documentation, which says to give a model explicit permission to admit uncertainty.

What a usable draft looks like

We wrote the draft below by hand to show the target. It is not a logged test result.

Subject: Your heat pump: new installation date and temporary heating

Dear Ms Bennett,

I’m sorry we didn’t get back to you sooner. Unfortunately we can’t keep the 12 November date, because our supplier won’t deliver the outdoor unit until the week of 23 November. The earliest we can install is Wednesday 2 December, and we’ll confirm the exact day once the unit has arrived.

Until then, we can lend you an electric heater free of charge. You can collect it, or we can bring it to you. We’ll get back to you about the cost of your fan heaters [OPEN: by when?].

Mr Hayes, our site manager, is available on extension 23.

Kind regards

How to check the draft

Read for facts first, then for tone.

  • Does every date match your notes exactly? 2 December is “earliest”, not fixed.
  • Is there a promise that wasn’t under FACTS? A sentence like “We’ll refund the fan heaters” has to go.
  • Does the draft answer every question? The cost question can stay open, but it can’t be missing.
  • Is there still an [OPEN] in the text? Settle it before the email goes out.

If something is off, follow up in the same chat instead of starting again: “Cut this to 90 words” or “Put collecting the heater first.”

Using it as a team template

The same structure works for complaints, late deliveries and questions about quotes. The CUSTOMER EMAIL, FACTS and DO NOT PROMISE blocks and the format stay the same. If someone writes these emails every day, they shouldn’t have to paste the fixed parts each time. In onAI, you can put this prompt into a custom agent and share it with customer service. Your team then only adds the email and the facts.

Try the prompt on a customer email you have to answer this week anyway, and notice which facts you forgot to give the AI the first time. Those lines belong in your team template.

Further reading