How to write a system prompt for a customer service bot

An AI chatbot on your website, WhatsApp or Instagram behaves according to its base instructions, the system prompt. It’s the text the bot reads before every conversation, defining who it is, what it knows and how it talks. A good one is the difference between a bot that solves problems and one that makes up your prices.

The parts of a support system prompt

1. Identity and tone

Who the bot is and how it sounds. “You are the virtual assistant for Maple Street Bakery. You’re friendly and brief, like a helpful person at the counter.” If your brand has a voice, this is where it goes.

2. Business facts (its source of truth)

Hours, delivery areas, prices, payment methods, return policy. Everything the bot can state with confidence. Then add the rule that matters most:

Use only this information for prices, hours and policies.
If asked something that isn't covered here, say so and offer
to connect the customer with a person. Never make things up.

Without it, the model fills gaps with details that sound plausible and aren’t true.

3. What it does in every conversation

The usual flow: greet, figure out what the customer needs, answer, take an order or booking (collecting name, time and any details), confirm.

4. What it never does

Give medical or legal advice, promise discounts that don’t exist, argue with an upset customer, ask for card numbers. Spell it out.

5. When to hand off to a human

Complaints, special orders, frustrated customers, anything outside its information. And how: “I’m passing this to our team. Someone will reply within 30 minutes during opening hours.”

6. Channel-appropriate formatting

Messaging apps aren’t web pages. Two or three short lines per message, no tables, one question at a time. When the customer has to choose, numbered options.

7. Sample conversations

Two or three realistic exchanges are gold. Include an easy one, one where the bot lacks the answer, and one off-topic:

Customer: Do you deliver to Oak Park?
Bot: We do! Delivery to Oak Park is $6 and takes about 45 minutes.
Want to place an order?

Customer: Are your croissants nut-free?
Bot: I can't confirm that, and I don't want to guess about allergies.
Let me connect you with our team so they can answer properly.

Common mistakes

Endless rules. A bot with five pages of instructions contradicts itself. Prioritize what happens every day.

Stale facts. When prices change, update the system prompt the same day.

Skipping the test run. Before real customers see it, play a difficult customer yourself: ask things it doesn’t know, push for a discount, change the subject.

Build it with the coach

In the coach, choose “Build a bot or assistant.” The questions switch to building a system prompt, with the safety rules included. To shape the bot’s personality, see how to give AI a role.