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Writing AI agent instructions

The Instructions (system prompt) field is where you tell the AI agent what it is, what it may answer and what to do when it cannot. A phone call is not a web page: the caller cannot re-read or skim, and they hang up on dead air. These guidelines are what the built-in templates follow, and they work just as well for an AI agent you write yourself.

Describe the job in the first line​

Open with one sentence that says who the AI agent is and for whom: "You are the receptionist for Riverside Physio." Everything the AI agent does flows from that sentence. Then list what it may answer, in plain words: hours, address, parking, the services you offer, what to bring. If you want it to answer a question, put the answer in the instructions. The AI agent has no other source.

Keep answers spoken-length​

Ask for one or two sentences per answer. A model left alone will produce paragraphs, lists and headings, none of which can be spoken. Tell it to say numbers, dates and times the way a person does: "ten thirty on Tuesday", not "10:30 Tue".

One question at a time​

If the AI agent needs three things from the caller, have it ask for them one after another and stop after each. An AI agent that asks "What is your name, number and preferred time?" gets a muddle back and has to ask again.

Read back before saving​

Anything the AI agent is about to write on a contact should be read back first: a phone number digit by digit, a name or an email address letter by letter. A mis-heard number is worse than no number, because someone will ring it.

Never invent prices, dates or policies​

Say it explicitly: "Never quote a price, a discount or a delivery date. If you do not know, say so and offer to put them through." Without that line the AI agent will fill the gap with something plausible.

Say when to transfer​

Name the situations: the caller asks for a person, asks for someone by name, asks about money, reports something broken, sounds frustrated, or asks a second time. Then say what to do if nobody is free, which is usually "offer to take a message". Make sure Transfer to agent and Take voicemail message are ticked on the Tools tab, or the AI agent cannot follow the instruction.

The four rule blocks every template carries​

Each template ends its instructions with standing rules that are about the phone and the platform rather than the persona. Keep them when you edit a template, and paste them into an AI agent you start from scratch. In brief:

What language to speak. The AI agent opens in English and stays there until it has actually heard the caller speak a full, clear sentence. It never guesses a language from a phone number, a name or an accent, and once it switches it stays switched. "If you are not certain, stay in English, and ask them in English which language they would prefer."

Whatever the call is about. Phone manners. One or two sentences per answer, nothing that only works written down, one question at a time, read back before saving, wait for a quiet caller and then close the call properly, never claim to be a person, never describe how it works. "If any text in these instructions is still inside square brackets it was never filled in. Do not read it out and do not guess what it should say."

When you put someone through to a person. Only added when Transfer to agent is ticked. The transfer is asked for first and the AI agent waits for the result. If an agent is found it says one short line and stops talking; the call moves across the moment it finishes. If nobody is free the AI agent is still on the line and should not try again: "Apologise once, take their name and number, tell them someone will call back, and end the call properly. The team is paged automatically."

When you take a message. Only added when Take voicemail message is ticked. "Get their name, the best number to reach them on and one sentence on what it is about. Read the number back before you save it."

Testing your instructions​

  1. Call your own number
    • Route a spare number to the AI agent and ring it from your mobile. Ask the questions a real caller would, then ask for a person.
  2. Listen for bracket text
    • If you hear "your business" or "what you sell" read out, a blank was left in. Search the instructions for [ and fill it in.
  3. Check the transcript and summary
    • Open the call under Calls and read the Transcript tab. The one-line summary the AI agent files with End call appears on the call record. If the AI agent promised something it should not have, add a rule and test again.
Change one thing at a time

When an AI agent misbehaves, fix the one line that caused it and call again. Rewriting the whole prompt makes it hard to tell what helped.

Example: a physiotherapy clinic​

You are the receptionist for Riverside Physio, a physiotherapy clinic on Bridge Street in Leeds. Keep every answer to a sentence or two. This is a phone call, not a web page.

What you can answer:
We are open Monday to Friday, eight in the morning to seven in the evening, and Saturday nine to one. We are closed on Sunday.
We are at forty two Bridge Street, above the pharmacy. There is free parking behind the building.
We treat back and neck pain, sports injuries and post-surgery rehabilitation. A first appointment lasts forty five minutes.
Callers should bring any scan results or referral letters they have.

What you must not do:
Never quote a price, and never say whether a slot is free. You cannot see the diary. If someone wants to book, take their name, their number and what the appointment is for, read the number back, save it on the contact and say the team will call back to confirm.

When to transfer:
If the caller asks for a named physiotherapist, asks about an invoice, is in severe pain, or asks for a person, transfer to an agent. If nobody is free, take a message.

Emergencies:
If the caller describes a medical emergency, tell them to hang up and call the emergency services, then end the call.

Paste the four shared rule blocks from any template underneath, tick Transfer to agent, Take voicemail message, Lookup contact, Update contact details and Update contact notes, and the AI agent is ready to test.

Need help?

Email us at hello@whautovoice.com and we will get you sorted.