Voice agent prompts: writing an AI receptionist script

Good voice agent prompts are the difference between an AI phone agent that callers put up with and one they barely notice. The prompt is the agent's brief: its role, its goals, the facts it can use and how to behave when a call goes sideways. This guide shows how to write one section by section, with a skeleton you can turn into your own AI receptionist script.

What is a voice agent prompt?

A voice agent prompt is the set of written instructions an AI phone agent works from on every call. It defines who the agent is, what it is trying to achieve, which facts it may rely on, how to handle each common type of call and when to pass the caller to a person. The model supplies language skills; the prompt supplies the job.

Most setups split that material in two: instructions describe behavior, and a knowledge section holds facts such as hours, services and policies. Keeping them apart makes updates safer, because new Saturday hours shouldn't mean touching the rules for an angry caller. If you are new to how the pieces fit together, start with our explainer on what an AI voice agent is.

Why writing for the ear is different

A phone agent's prompt is not a chatbot prompt with a voice bolted on. People on a call can't scroll back, can't see bullet points and lose track after two or three pieces of information. The prompt has to tell the agent to talk the way a good receptionist talks:

• Short turns. One or two sentences, then let the caller respond.
• One question at a time. "What's your name, number and address?" becomes three separate questions.
• No formatting. The agent should never read out bullets, headings or symbols.
• Spoken numbers. Phone numbers in groups, times as "ten thirty in the morning", prices the way a person would say them.
• Everyday words. Contractions and plain phrasing sound natural; formal written phrasing sounds like a recording.
• Room to think. Callers need a moment to find a calendar or an account number, so the agent shouldn't fill every pause.

The parts of an AI receptionist script

Most strong prompts follow the same order. The skeleton below uses a fictional plumbing company, Riverside Plumbing; swap in your own details. Each part can be a short paragraph or a handful of lines.

1. 1

   Role and persona

   Who the agent is and how it sounds. Example: You are the phone receptionist for Riverside Plumbing. You are calm, friendly and brief, like a helpful local office.

2. 2

   Goal of every call

   What success looks like. Example: Find out what the caller needs, answer simple questions, book service visits and get urgent problems to the on-call plumber.

3. 3

   Opening line

   The first thing callers hear. Example: Thanks for calling Riverside Plumbing, this is the automated assistant. How can I help? Keep it under ten seconds and invite the caller to talk.

4. 4

   Business facts

   Hours, service area, services, jobs you don't take and any prices you are happy to quote. Add a fallback: If the answer is not in these facts, say you will find out and offer to take a message.

5. 5

   Call flows

   A short section for each common call type: how to recognize it, what to ask and in what order, and what to do at the end.

6. 6

   Booking rules

   Which slots it may offer, how far ahead, how long each job type takes and which details every booking needs.

7. 7

   Confirmation rules

   Which details to read back before acting, and how to say them so mistakes are easy to hear.

8. 8

   Handoff rules

   When to transfer, when to take a message, when to offer a callback, and who receives each one.

9. 9

   Never say

   Topics and promises that are off-limits, from diagnosing faults to guaranteeing arrival times.

10. 10

    Closing

    How to finish: recap what happens next, mention any text the caller will receive, and say goodbye without dragging it out.

How do you write call flows for common calls?

Write call flows by listing the five or six reasons people call you most, then describing each as a short sequence: how to recognize it, what to ask, what to do and how to finish. Take the reasons from your call history, not from memory. Here is one flow from the plumber's prompt:

1. Recognize it. The caller wants a plumber to visit for something non-urgent, such as a slow drain or a dripping tap.
2. Ask, one at a time. Their name, the service address, the best callback number and a short description of the problem.
3. Check the area. If the address is outside the service area, say so politely and offer to pass a message to the office.
4. Offer times. Offer two open slots from the calendar; if neither works, offer the next two.
5. Confirm and book. Read back the name, address, number and time, then book and say a text confirmation is coming.
6. Finish. Ask whether there is anything else, then end the call.

The flow sets the order and the checkpoints but leaves out exact wording, so the agent can phrase things naturally. Flows that dictate every sentence sound stiff and break when a caller answers two questions at once.

How should a voice agent handle interruptions?

A voice agent should stop talking as soon as the caller interrupts, listen, and respond to what was just said instead of resuming its half-finished sentence. Say this explicitly in the prompt, and tell the agent never to ask again for details the caller already gave. Part of this behavior is a setting on the voice platform, so check both.

• Barge-in: If the caller starts talking, stop and listen. Do not restart your previous sentence.
• Answers out of order: If the caller gives details before you ask, accept them and skip those questions.
• Silence: If the caller goes quiet, ask once whether they are still there. If there is no reply, say goodbye and end the call.
• Unclear speech: If you missed something, ask the caller to repeat only that part.
• Topic changes: If the caller switches subject, handle the new request, then return to any unfinished booking.

Confirming details back to the caller

Speech recognition is very good and still mishears things, especially surnames, house numbers and phone digits on a weak signal. Confirmation rules catch those errors while the caller is still on the line. Tell the agent what to read back and how:

• Spell uncommon names back letter by letter and invite the caller to correct any letter.
• Read phone numbers in groups of three, three and four.
• Say dates with the weekday, as in "Tuesday the fourteenth", so a wrong date stands out.
• Repeat house numbers digit by digit, since fifteen and fifty are easy to confuse.
• Confirm once at the end of a section, not after every single answer.

Confirm before acting, not after. Booking the wrong Tuesday and apologizing later costs far more than ten seconds of reading back.

Handoff rules and things the agent should never say

Handoff rules decide when the agent steps aside. Write them as plain triggers and actions, for example: If the caller asks for a person, transfer to the office line during opening hours; otherwise take a message for a callback the next morning. Typical triggers are a direct request for a human, an emergency, a complaint, a billing dispute and anything still unresolved after two attempts.

A never-say list matters just as much. Keep it short and specific:

• Prices, discounts or arrival times that aren't in its information.
• Diagnoses, legal opinions, medical advice or anything that sounds like professional judgment.
• Details about other customers, their appointments or staff schedules.
• Promises the business hasn't approved, such as "we'll definitely fix it today."
• Any claim to be a person. If asked, it says it is an automated assistant.

How do you test a voice agent prompt?

Test a voice agent prompt by running a fixed set of scripted calls that cover your main flows and your hardest edge cases, then reading every transcript line by line. Look for what it should have asked and didn't, as well as what it said. A starting test set:

1. A plain booking from start to finish.
2. A caller who gives every detail in one breath.
3. A caller with an unusual surname and a noisy background.
4. A question the prompt doesn't cover.
5. A caller who asks for a person in the first sentence.
6. An emergency described vaguely, such as "there's water coming through the ceiling."
7. A caller who changes their booking halfway through.

Keep those calls as a regression set: fix one thing, rerun them all and confirm nothing else broke. After launch, real calls become the best test material: every Calldone call is saved with its audio, a written transcript, a short summary and the result, which shows exactly where the script needs work. Our AI receptionist setup guide covers the rest of the launch process.

Common prompt mistakes to avoid

• Pasting the whole website. Pages of unedited text bury the facts the agent needs. Summarize them.
• Conflicting rules. "Always book the first open slot" and "never book same-day jobs" will collide. Read the prompt for contradictions.
• Stacked questions. Asking for three details at once leads to missed answers.
• No exit. Every flow needs an ending, or the agent keeps asking whether there is anything else.
• Untested languages. If customers call in Spanish or other languages, test those calls too; our guide to bilingual answering explains what to check.

A prompt is never finished. Services change, callers surprise you and new questions appear. Treat the script like a training manual for a new AI receptionist: written carefully, reviewed often and updated whenever a real call exposes a gap.