Assistant

managerial-maroon · 2025-06-10T04:53:06.142Z

Hey there, How can I get my assistant to receive a call from a customer and then transfer that call to a specific number — one of the numbers registered in the transfer_call function that I want? If you can help me with this problem, I'd definitely appreciate it. Thanks!

V

Vapi Support BotAPP•6/10/25, 4:54 AM

To have your assistant receive a call and transfer it to a specific registered number, add the

transferCall

transferCall

tool to your assistant with your desired numbers:

{
  "tools": [
    {
      "type": "transferCall",
      "destinations": [
        { "type": "number", "number": "+1234567890", "message": "I am forwarding your call to Department A. Please stay on the line." }
      ],
      "function": { "name": "transferCall" }
    }
  ]
}

{
  "tools": [
    {
      "type": "transferCall",
      "destinations": [
        { "type": "number", "number": "+1234567890", "message": "I am forwarding your call to Department A. Please stay on the line." }
      ],
      "function": { "name": "transferCall" }
    }
  ]
}

{
  "tools": [
    {
      "type": "transferCall",
      "destinations": [
        { "type": "number", "number": "+1234567890", "message": "I am forwarding your call to Department A. Please stay on the line." }
      ],
      "function": { "name": "transferCall" }
    }
  ]
}

{
  "tools": [
    {
      "type": "transferCall",
      "destinations": [
        { "type": "number", "number": "+1234567890", "message": "I am forwarding your call to Department A. Please stay on the line." }
      ],
      "function": { "name": "transferCall" }
    }
  ]
}

In your system prompt, instruct the assistant when to use each number (e.g., "If the user asks for sales, call the

transferCall

transferCall

function with

+1234567890

+1234567890

+1234567890

+1234567890."). This will let your assistant transfer calls to the specific number you want.
Reference: Vapi call forwarding documentation

Source:

Vapi Call Forwarding Documentation

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

E

extreme-purple•6/10/25, 6:13 AM

Register phone numbers using the transferCall tool in your assistant’s config, then trigger the transfer by calling the function with the desired number, for dynamic routing, use a webhook to select the destination at runtime based on the conversation..

M

managerial-maroonOP•6/10/25, 6:28 AM

Hi @Kings_big

Thanks for reaching out to me.
Could you send some sample code?

Mmanagerial-maroon Hi @Kings_big💫 Thanks for reaching out to me. Could you send some sample code?

E

extreme-purple•6/10/25, 6:32 AM

Review the doc

https://docs.vapi.ai/calls/call-dynamic-transfers

Dynamic Call Transfers | Vapi

M

managerial-maroonOP•6/10/25, 6:41 AM

Hmm, actually, I've tried this content but it is definitely not working.

M

managerial-maroonOP•6/10/25, 6:48 AM

Did you try like this once?

E

extreme-purple•6/10/25, 7:10 AM

To register numbers for transferCall, add them in your assistant config, then call transferCall(number) in your logic, or use a webhook to choose the number dynamically at runtime.

// Assistant config
{
"tools": {
"transferCall": {
"enabled": true,
"phoneNumbers": {
"support": "+12585",
"sales": "+198765"
}
}
}
}

// Static call transfer
if (intent === 'speak_to_support') {
transferCall('+125');
}

// Dynamic routing via webhook
const res = await fetch('https://yourserver.com/get-transfer-number', {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ userIntent: currentIntent })
});
const { phoneNumber } = await res.json();
transferCall(phoneNumber);

M

managerial-maroonOP•6/10/25, 7:19 AM

"tools": [
          {
            "id": "-------------------------------------",
            "createdAt": "2025-05-31",
            "updatedAt": "2025-06-10",
            "type": "transferCall",
            "function": {
              "name": "transfer_call_tool",
              "parameters": {
                "type": "object",
                "required": [],
                "properties": {}
              },
              "description": "trigger a live call transfer to a human agent"
            },
            "messages": [],
            "orgId": "000000000000000000000",
            "destinations": [
              {
                "type": "number",
                "number": "+11111111",
                "message": "I am forwarding your call to Department A. Please stay on the line.",
                "description": "Department A",
                "transferPlan": {
                  "mode": "blind-transfer",
                  "sipVerb": "refer"
                },
                "numberE164CheckEnabled": true
              }
            ]
          }
        ]

"tools": [
          {
            "id": "-------------------------------------",
            "createdAt": "2025-05-31",
            "updatedAt": "2025-06-10",
            "type": "transferCall",
            "function": {
              "name": "transfer_call_tool",
              "parameters": {
                "type": "object",
                "required": [],
                "properties": {}
              },
              "description": "trigger a live call transfer to a human agent"
            },
            "messages": [],
            "orgId": "000000000000000000000",
            "destinations": [
              {
                "type": "number",
                "number": "+11111111",
                "message": "I am forwarding your call to Department A. Please stay on the line.",
                "description": "Department A",
                "transferPlan": {
                  "mode": "blind-transfer",
                  "sipVerb": "refer"
                },
                "numberE164CheckEnabled": true
              }
            ]
          }
        ]

"tools": [
          {
            "id": "-------------------------------------",
            "createdAt": "2025-05-31",
            "updatedAt": "2025-06-10",
            "type": "transferCall",
            "function": {
              "name": "transfer_call_tool",
              "parameters": {
                "type": "object",
                "required": [],
                "properties": {}
              },
              "description": "trigger a live call transfer to a human agent"
            },
            "messages": [],
            "orgId": "000000000000000000000",
            "destinations": [
              {
                "type": "number",
                "number": "+11111111",
                "message": "I am forwarding your call to Department A. Please stay on the line.",
                "description": "Department A",
                "transferPlan": {
                  "mode": "blind-transfer",
                  "sipVerb": "refer"
                },
                "numberE164CheckEnabled": true
              }
            ]
          }
        ]

"tools": [
          {
            "id": "-------------------------------------",
            "createdAt": "2025-05-31",
            "updatedAt": "2025-06-10",
            "type": "transferCall",
            "function": {
              "name": "transfer_call_tool",
              "parameters": {
                "type": "object",
                "required": [],
                "properties": {}
              },
              "description": "trigger a live call transfer to a human agent"
            },
            "messages": [],
            "orgId": "000000000000000000000",
            "destinations": [
              {
                "type": "number",
                "number": "+11111111",
                "message": "I am forwarding your call to Department A. Please stay on the line.",
                "description": "Department A",
                "transferPlan": {
                  "mode": "blind-transfer",
                  "sipVerb": "refer"
                },
                "numberE164CheckEnabled": true
              }
            ]
          }
        ]

M

managerial-maroonOP•6/10/25, 7:19 AM

This is my assistant config

M

managerial-maroonOP•6/10/25, 7:20 AM

But I am curious how can I set phoneNumber key in that?

M

managerial-maroonOP•6/10/25, 7:20 AM

I can't phoneNumber field

M

managerial-maroonOP•6/10/25, 7:33 PM

@Kings_big

M

managerial-maroonOP•6/10/25, 7:33 PM

Can you help me plz?

V

VapiAPP•6/10/25, 8:30 PM

looking into it.

D

dangerous-fuchsia•6/10/25, 8:50 PM

Hey @Aurelius !

You're actually doing it correctly - your assistant config looks perfect!

You don't need to manually define the function parameters. Just having the function name and destinations is enough. Vapi automatically handles the parameter structure.

Here's how the transfer mechanism works:

Your config (which is correct):

{

  "type": "transferCall",

  "function": {

    "name": "transfer_call_tool"

  },

  "destinations": [

    {

      "type": "number",

      "number": "+11111111",

      "message": "I am forwarding your call to Department A...",

      "description": "Department A"

    }

  ]

}

{

  "type": "transferCall",

  "function": {

    "name": "transfer_call_tool"

  },

  "destinations": [

    {

      "type": "number",

      "number": "+11111111",

      "message": "I am forwarding your call to Department A...",

      "description": "Department A"

    }

  ]

}

{

  "type": "transferCall",

  "function": {

    "name": "transfer_call_tool"

  },

  "destinations": [

    {

      "type": "number",

      "number": "+11111111",

      "message": "I am forwarding your call to Department A...",

      "description": "Department A"

    }

  ]

}

{

  "type": "transferCall",

  "function": {

    "name": "transfer_call_tool"

  },

  "destinations": [

    {

      "type": "number",

      "number": "+11111111",

      "message": "I am forwarding your call to Department A...",

      "description": "Department A"

    }

  ]

}

To trigger the transfer, add this to your system prompt:

When the user asks to speak with a human agent or Department A, call the transfer_call_tool function with the phone number "+11111111".

When the user asks to speak with a human agent or Department A, call the transfer_call_tool function with the phone number "+11111111".

When the user asks to speak with a human agent or Department A, call the transfer_call_tool function with the phone number "+11111111".

When the user asks to speak with a human agent or Department A, call the transfer_call_tool function with the phone number "+11111111".

That's it! Your assistant will automatically call the function when appropriate, and Vapi handles the rest. The confusion earlier was from incorrect examples - ignore the "phoneNumber" field stuff, it doesn't exist.

M

managerial-maroonOP•6/21/25, 11:21 AM

@Kings_big

M

managerial-maroonOP•6/21/25, 11:21 AM

Hello

M

managerial-maroonOP•6/21/25, 11:21 AM

I am integrating the calendar using VAPI

M

managerial-maroonOP•6/21/25, 11:22 AM

but assistant bot currently recognizes the date as 2023.

E

extreme-purple•6/21/25, 11:48 AM

Ensure your prompt includes Current date: {{ "now" | date: "%B %d, %Y", "UTC" }}, use a tool step to check the real-time date before bookings, and send dates in proper ISO format using parseDate and formatDate..

M

managerial-maroonOP•6/21/25, 12:39 PM

Thanks for your answer.
And Do I have to add this prompt at the Assistant prompt or Calendar event tools?

M

managerial-maroonOP•6/21/25, 1:04 PM

I've tried that but it doesn't still work.

V

VapiAPP•6/21/25, 10:11 PM

Add

{{ "now" | date: "%Y-%m-%d", "UTC" }}

{{ "now" | date: "%Y-%m-%d", "UTC" }}

{{ "now" | date: "%Y-%m-%d", "UTC" }}

{{ "now" | date: "%Y-%m-%d", "UTC" }} to the assistant prompt not the calendar tool, and in Make.com, use a tool step to get the current date and format it with

parseDate

parseDate

parseDate

parseDate and

formatDate

formatDate

formatDate

formatDate before sending to the calendar in ISO format..

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