Short answer: An AI phone agent should hand a call to a person when the caller asks for one, when the request is outside what the agent is allowed to do, when it has failed to understand twice, or when the call involves risk such as a complaint, a payment dispute or a health question. A good handoff is "warm": the person who picks up already sees who is calling, why, what the agent has done, and a transcript, so the caller does not repeat themselves. Every handoff should be logged with its reason and outcome, because those logs show you what to fix next.
This applies whether you call the product an AI answering service, an AI call assistant, an AI receptionist or an AI IVR. The technology is similar. The handoff design is what separates one that customers tolerate from one they hang up on.
What an AI phone agent should do, and what it should pass on
A useful way to decide is to sort calls into three groups before you build anything:
| Call type | Examples | Agent's role |
|---|---|---|
| Fully automatable | Opening hours, order status, booking or moving an appointment, simple product questions | Answer and act, using real data from your systems |
| Assist then hand off | Demo requests, new sales enquiries, complex orders, returns with exceptions | Collect details, qualify, then transfer or book a callback |
| Hand off immediately | Complaints, payment disputes, legal or medical questions, distressed callers, anyone who asks for a person | Transfer straight away with a short summary |
Our AI voice receptionist guide covers the first group in detail. For online stores, where order lookups make up much of the volume, see voice AI for Shopify brands. The handoff rules for the other two groups are where most projects need the most care.
When to transfer: write the triggers down
Handoff triggers belong in a written specification, not only in the agent's prompt. Typical triggers:
- The caller asks for a person. Always honour it, at most after one offer to help ("I can check that order now, or I can put you through to the team. Which would you prefer?").
- Out of scope. Anything the agent is not permitted to do, for example issuing refunds above a set limit or changing contract terms.
- Repeated misunderstanding. Two failed attempts to understand the same request is a common rule. A third attempt rarely goes better.
- Risk words or sentiment. Complaints, cancellations, threats of legal action, medical symptoms, or a caller who sounds distressed.
- Tool failure. If the order system or calendar is down, the agent should say so honestly and transfer or take a message, rather than guess.
Writing the triggers down also gives you a test list. Our article on governed AI agents describes the wider controls (scope, approvals, logging, a named owner) that the handoff is part of.
Warm transfer, cold transfer and callbacks
| Method | How it works | When to use |
|---|---|---|
| Cold transfer | Call is passed straight to a number or queue | Simple routing, when the receiving team does not need context |
| Warm transfer | Agent briefs the person (spoken or on screen) before connecting the caller | Sales enquiries, complaints, anything where repeating details annoys the caller |
| Callback | Agent books a time or creates a ticket; a person calls back | After hours, busy periods, or when no one is available to take the transfer |
| Message only | Agent records details and sends them on | Last resort, when nothing else is possible |
On the telephony side, transfers between systems often use the SIP protocol. A common method is the SIP REFER request, defined in RFC 3515, which asks the other side to connect the call to a new destination. Some carriers and contact-centre platforms can also carry a small amount of call data in SIP headers, for example the User-to-User header defined in RFC 7433. Whether you can use these depends on your carrier and phone system, so check with them early.
Passing context so nobody repeats themselves
The caller's experience of a handoff is simple: did the person who answered already know why I was calling? To make the answer yes, send these with every transfer:
- Caller's number and, if identified, their name and customer record.
- The reason for the call in one sentence.
- What the agent has already done (looked up order 123, offered a reschedule, caller declined).
- Why it is transferring (caller asked, out of scope, two failed attempts, complaint).
- The full transcript, or a link to it.
- Any data the agent collected (address, preferred time, product).
There are three common ways to deliver it: a screen pop in the helpdesk or CRM when the call arrives, a short spoken whisper to the person before the caller is connected, or a ticket created at the moment of transfer that the person opens. A screen pop or ticket is usually the most reliable, because it also leaves a record.
Phone numbers and carrier connectivity
Before choosing a voice platform, decide where the phone number lives:
- Platform numbers. The quickest start: the voice platform provides a number and handles the line. Moving away later may mean porting the number or changing it.
- Bring your own carrier. You keep your existing numbers with your carrier or cloud phone system and connect the voice platform through a SIP trunk. More setup, but you keep control and can route calls between the AI and your team inside one phone system.
- Forwarding. Your existing number forwards to the AI after hours or after a set number of rings. Simple, and a good way to start small.
Ask any platform: can I use my own numbers, which countries does it support, and how does a transfer back to my team work technically? Our comparison of voice AI platforms covers some of the differences.
Outcome logging: what to record after every call
If you cannot see what happened on calls, you cannot improve the agent. Log, for every call:
| Field | Why it matters |
|---|---|
| Call reason (category) | Shows which requests are most common |
| Resolved by agent, transferred, callback, or abandoned | The core outcome measure |
| Transfer reason | Shows where the agent's scope or understanding falls short |
| Time to transfer | Long times before transfer frustrate callers |
| Outcome after transfer | Did the person resolve it? Was the context useful? |
| Transcript and recording link | For review and for fixing specific failures |
Review a sample of transferred calls every week. If one transfer reason dominates, that is your next improvement. Keep recordings and transcripts only as long as you need them, tell callers that calls may be recorded, and make sure your voice platform has a processor agreement if you handle personal data in the EU.
Special cases: health, payments and regulated calls
Some calls carry extra legal duties. Healthcare appointment lines may handle protected health information; our guide to voice AI in healthcare scheduling covers what that changes. Card payments should not be read out to an AI agent unless the payment flow is designed and certified for it; transfer to a compliant payment process instead. When in doubt, the safest design is for the agent to collect the reason for the call and hand over quickly.
Start small
The lowest-risk start is an after-hours line: the agent answers when nobody else can, handles the simple requests, and books callbacks for the rest. Once the logs show how it handles real calls, widen its scope. You can hear a grounded assistant on our voice AI demo, and the voice AI page explains how we build them.
Frequently asked questions
When should an AI phone agent transfer to a human? When the caller asks for a person, when the request is outside what the agent may do, after two failed attempts to understand, when the call involves a complaint, payment dispute, legal or medical question, or when a system it depends on is down.
What is a warm transfer? A transfer where the person receiving the call is briefed before the caller is connected, either by a short spoken summary or by details on screen. The caller does not have to repeat themselves.
How does an AI agent pass the transcript to a human? Usually through the helpdesk or CRM: a ticket or screen pop created at the moment of transfer, with the summary, the actions taken, the transfer reason and the transcript or a link to it. Some phone systems can also carry a small amount of data in SIP headers.
Can I keep my existing phone number with an AI answering service? Often yes. You can forward calls to the AI, or connect the voice platform to your existing carrier through a SIP trunk. Check which method each platform supports and how transfers back to your team work.
What should I log after AI-handled calls? The call reason, whether it was resolved, transferred, called back or abandoned, the transfer reason, the time to transfer, the outcome after transfer, and a link to the transcript and recording. Review transferred calls weekly.
Is an AI IVR the same as an AI voice agent? They overlap. A traditional IVR routes calls with menus and keypad choices. An AI IVR or voice agent understands natural speech, can answer and act on simple requests, and routes the rest. Both need clear transfer rules.