When a call is transferred, the key question is whether the person who answers already knows the reason for the call. With a warm transfer, the recipient is informed before the connection is made; with a cold transfer, the caller must start their explanation from the beginning. According to ElevenLabs, this choice affects the handling time, the first-contact resolution rate, and can even change the score customers give their support experience.
The difference lies in the amount of information conveyed at the moment of transfer. The warm transfer, also called a warm handoff or attended transfer, allows the operator to brief the recipient, via a live introduction or a brief summary, before connecting the caller. The cold transfer, also known as a blind transfer, connects the caller directly, without the recipient receiving any prior information.
Between the two exists the tepid transfer: the operator dials the destination number and connects the caller as soon as someone answers, without a conference or introduction. According to the source, some real-world implementations fall into this intermediate category.
A warm transfer typically follows five steps. The operator, human or AI agent, decides another person is needed, then informs the caller who they will be transferred to. They then call the recipient while the caller waits, provide them with a summary of the issue, then connect both parties and leave the line. The source emphasizes that the summary step is what makes the transfer “warm”: without it, the sequence becomes a tepid or cold transfer.
When to choose one or the other
The choice involves weighing the transfer against the cost of lost context. A warm transfer takes more time, but is justified when repetition would frustrate the caller. A cold transfer, being faster, is suitable for simple calls.
According to the source, warm transfers are suited for complex issues, such as billing disputes or technical escalations, for sensitive conversations, like complaints, cancellations, or health and finance matters, as well as for high-value customers. Cold transfers are suitable for simple routing to the correct department, for queues and high-volume lines, where speed trumps context.
Whichever method is used, the source recommends writing a short summary, stating in one or two sentences who is calling, what they are asking for, and what has already been tried. It also insists on planning a fallback solution, as recipients do not always answer, and on verifying information already provided, such as identity or account number, to avoid asking for it again.
Transfers in ElevenAgents
In ElevenAgents, AI voice agents transfer calls using the transfer_to_number tool, triggered when a defined condition is met, for example when a caller asks to speak to a human. This tool offers three transfer types. The Conference Transfer, the default, dials the number, adds the recipient to a conference and then leaves the line; on the native Twilio integration, it reads a transfer message to the human operator. The Blind Transfer directs the call without a prior message and retains the caller ID. The SIP REFER Transfer, reserved for SIP calls, also does not include a message.
The warmth of the transfer relies on two parameters. The client_message corresponds to what the caller hears while on hold, while the agent_message constitutes the summary given to the operator. The source illustrates this distinction: the caller hears “I’m connecting you with a billing specialist,” and the specialist receives the following message: “The caller was charged twice on their March bill and wants a refund for the duplicate charge.” For transfers from one AI agent to another, the platform offers the transfer_to_agent tool.
In case of no answer, the behavior varies by transfer type. With Conference Transfer, the agent stays in the conference until the recipient answers. With Blind Transfer, it disconnects immediately and can no longer intervene. With SIP REFER, the fallback solution must be configured on the company’s SIP trunk or PBX. The source finally notes that the caller’s experience depends on the configuration of the telecom operator, SIP trunk, or phone system, and recommends verifying it before going live.
