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Nappai Documentation

Transfer Call

Transfer Call is a tool for the Voice Agent: it passes the live call to another NappAI voice agent, a phone number or a SIP address. It connects to the Tools connector of the Voice Agent, or of a sub-agent, and the agent decides when to use it from your System Prompt and the node’s description.

The caller first hears the transfer announcement and a short tone, which you can turn off. If you pass the call to another agent, the new agent carries on the same conversation: it knows what has been said and why, so it does not ask again for what was already said. The full guide, including the trunks you need to transfer to a phone, is in Transfers and hanging up.

When to use it

  • Building a switchboard: a receptionist that passes calls to finance, support or sales, each with its own agent.
  • Passing to a team member the cases the agent cannot solve.
  • Briefing an advisor on the case before putting the customer through.
  • Routing calls to an emergency phone line.

Configuration

In fields that support tool mode, tool mode decides who writes the value: on, the AI writes it on each call; off, the fixed text you type here is used. Destination, Announcement To The Caller and Reason support tool mode.

FieldWhat it does
Destination Typephone (default) passes the call to a number or a SIP address. voice_agent passes it to another NappAI voice agent, in the same call and with the conversation so far.
Announcement To The CallerWhat the caller hears as soon as the transfer starts, word for word and in the language they are speaking. Fixed, or in tool mode written by the agent on each call.
ReasonWhy the call is being transferred. The agent writes it and the destination receives it.
Transfer ToneOn (default), once the announcement ends a short tone plays until the call is handed over, so the caller does not wait in silence; it never plays over the announcement. With warm, both sides also hear it when they are connected. Off, there is silence after the announcement until the call is handed over.

With Destination Type set to voice_agent

FieldWhat it does
Voice AgentAnother of your flows with a Voice Agent in it. Press the refresh button to list them. The call goes to that flow’s published version, also when you test from the playground, so publish it first.

With Destination Type set to phone

FieldWhat it does
DestinationThe number in international format, for example +34600000000, or a SIP address.
Typecold (default) passes the call straight away. warm puts the caller on hold with music, calls the destination person, briefs them on the case and only connects them if they accept.
Ring Timeout (Seconds)Only with warm. How long the destination person may take to answer. After that, the caller goes back to the agent. From 10 to 180; default: 45.
Advisor Reply Timeout (Seconds)Only with warm. Once the agent has spoken to whoever answered, how long it waits for a reply. If they say nothing (a voicemail, nobody there), the caller is back with the agent. From 5 to 60; default: 15.
Hold Limit (Seconds)Only with warm. The longest the caller waits in total, ringing and briefing included. After that, the transfer is dropped and the agent carries on with them. From 60 to 600; default: 180.
Advisor LanguageOnly with warm. The language the agent uses to brief the destination person, for example Spanish or English. Empty, the language the caller spoke.
Advisor Briefing InstructionsOnly with warm. How the agent talks to the person it calls before putting the caller through. It comes filled with a default text you can change, for example to ask for more formality. The conversation, language and reason are added automatically.

Output

The Transfer output is the tool. Connect it to the Tools connector of the Voice Agent or of a sub-agent.

If the destination does not answer, rejects the call or is not available, the agent tells the caller and the call stays with it.

Example

A utility company wants its receptionist to pass invoice questions to the finance agent.

  1. Create and publish the finance agent.
  2. In the reception agent, add a Transfer Call and connect it to Tools.
  3. Choose voice_agent in Destination Type and the finance agent in Voice Agent.
  4. Leave Announcement To The Caller in tool mode so the agent says something like “I’ll put you through to finance, one moment”.
  5. In the System Prompt write: “If they ask about invoices or payments, transfer to finance”.
  6. Test in the playground by asking about an invoice.

Good practices

  • Add one Transfer Call per destination and describe in each node when to use it: the agent chooses from that description.
  • Leave the announcement in tool mode if you want it to sound natural; fix it only when the exact words matter.
  • Use warm when the person answering needs context, and let your team know the agent will speak to them when they pick up.
  • Do not ask the agent to put sensitive data in Reason: it travels to the destination.