in transferCall, do i need to specify parameters ? Is it essential ?

I

Hi

V

Yes, specifying parameters—especially the
destination
destination
destination
destination parameter—is essential for
transferCall
transferCall
to work. Without it, the call will not be forwarded. Here’s a minimal example:

"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+1234567890"], // Replace with your number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+1234567890"], // Replace with your number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+1234567890"], // Replace with your number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+1234567890"], // Replace with your number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

Be sure to include this in your tool configuration for successful call transfers.

Sources:

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

VVapi Support Bot **Yes, specifying parameters—especially the `destination` parameter—is essential...

D

DuckieAPP•5/22/25, 5:24 PM

Message marked as helpful by @Hans!

VVapi Support Bot **Yes, specifying parameters—especially the `destination` parameter—is essential...

D

DuckieAPP•5/22/25, 5:24 PM

Message marked as helpful by @Hans!

I

instant-harlequin•5/22/25, 5:26 PM

But call is actually forwarded without parameter specification.
It 's strange

E

extreme-purple•5/22/25, 5:48 PM

Send your call id

Eextreme-purple Send your call id

I

instant-harlequin•5/22/25, 5:54 PM

You mean tool id ?

906508b3-fc46-4e57-86b8-22d53e39f44d

If it 's not this, how can i get call id ?

I

instant-harlequin•5/22/25, 5:58 PM

Here goes screenshot of agent
I gave system prompt details

Is vapi.ai smart enough to redirect call without

parameters

parameters

parameters

parameters config ?
Or am I going something wrong ?

E

extreme-purple•5/22/25, 6:17 PM

Vapi can redirect calls without explicit parameters, but proper configuration with defined destinations and messages is recommended for reliable forwarding.

Eextreme-purple Vapi can redirect calls without explicit parameters, but proper configuration wi...

I

instant-harlequin•5/22/25, 9:05 PM

I have found issue in Messages panel
In this example, we can add multiple request-start messages with condition for several phone numbers

But in UI, we can add only 1 message for message type.

V

VapiAPP•5/23/25, 4:51 AM

Hey Hana, checking if this is resolved/solved for you?

I

instant-harlequin•5/27/25, 3:10 PM

Yes, it 's solved

V

Vapi Support BotAPP•5/27/25, 3:12 PM

For reliable call forwarding in Vapi, always specify the
destination
destination
destination
destination parameter in your
transferCall
transferCall
function, even if calls appear to work without it. This ensures predictable behavior, especially as your configuration grows. Example:

{
  "function": {
    "name": "transferCall",
    "parameters": {
      "destination": "+15308891500"
    }
  }
}

{
  "function": {
    "name": "transferCall",
    "parameters": {
      "destination": "+15308891500"
    }
  }
}

{
  "function": {
    "name": "transferCall",
    "parameters": {
      "destination": "+15308891500"
    }
  }
}

{
  "function": {
    "name": "transferCall",
    "parameters": {
      "destination": "+15308891500"
    }
  }
}

This approach avoids ambiguity and supports custom messages and transfer plans per destination.

Sources:

V

Vapi Support BotAPP•5/27/25, 3:12 PM

For reliable call forwarding in Vapi, always specify the
destination
destination
destination
destination parameter in your
transferCall
transferCall
tool configuration.
Here's a recommended example:

{
  "function": {
    "name": "transferCall",
    "parameters": {
      "destination": "+15308891500"
    }
  }
}

{
  "function": {
    "name": "transferCall",
    "parameters": {
      "destination": "+15308891500"
    }
  }
}

{
  "function": {
    "name": "transferCall",
    "parameters": {
      "destination": "+15308891500"
    }
  }
}

{
  "function": {
    "name": "transferCall",
    "parameters": {
      "destination": "+15308891500"
    }
  }
}

This ensures your call is routed as intended, regardless of any fallback behaviors Vapi may apply if parameters are omitted.

Sources:

V

VapiAPP•5/28/25, 3:20 AM

Glad the issue was resolved. Please reach out to us if you have any other questions regarding this issue

Lltd-scarlet **For reliable call forwarding in Vapi, always specify the `destination` paramet...

S

sacred-emerald•6/21/25, 12:47 AM

Where do you specify this since you dont have access to that request when invoking the transfer call tool?

V

VapiAPP•6/23/25, 8:04 PM

This ticket has been marked as solved, and as a result, you will no longer receive any further responses. Kindly create a new support ticket to escalate your inquiry. 

in transferCall, do i need to specify parameters ? Is it essential ?

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