Hello, I am trying to pass an id when calling a VAPI phone number. I have figured I can use DTMF digits and call a Twilio phone number like that: "+14155161111,123" (where the id I want to pass to the assistant is

123

) I read that VAPI currently does not handle DTMF digits, so I figured I could use TWIML to handle that and reroute the call to VAPI. I have two Twilio endpoints now. The example code gathers three digits and redirects the call to VAPI:

/api/twilio/call

import { NextResponse } from "next/server";
const VoiceResponse = require("twilio").twiml.VoiceResponse;

export async function POST(): Promise<Response> {
  const twiml = new VoiceResponse();

  twiml.gather({
    numDigits: 3,
    method: "POST",
    action: `${process.env.NEXT_PUBLIC_VAPI_SERVER_URL}/api/twilio/gather`,
  });

  twiml.redirect(
    {
      method: "POST",
    },
    "https://api.vapi.ai/twilio/inbound_call",
  );

  console.log("twiml", twiml.toString());

  return new NextResponse(twiml.toString(), {
    headers: {
      "Content-Type": "text/xml",
    },
  });
}

/api/twilio/gather

import { NextResponse } from "next/server";
const VoiceResponse = require("twilio").twiml.VoiceResponse;

export async function POST(req: Request): Promise<Response> {
  const formData = await req.formData();

  console.log("Digits", formData.get("Digits"));

  const twiml = new VoiceResponse();

  twiml.redirect(
    {
      method: "POST",
    },
    "https://api.vapi.ai/twilio/inbound_call",
  );

  return new NextResponse(twiml.toString(), {
    headers: {
      "Content-Type": "text/xml",
    },
  });
}

*Problem*: after I gather digits, call status changes from

ringing

to

in-progress

. That leads to a

400

error from VAPI:

{
  "message": [
    "CallStatus must be one of the following values: ringing"
  ],
  "error": "Bad Request",
  "statusCode": 400
}

How can I solve this issue. Any other solutions for passing the id to the app is helpful.

The reason for the 400 error you're seeing is that VAPI expects incoming calls to have a "ringing" status, but after gathering DTMF digits, Twilio changes the call status to "in-progress". This is standard Twilio behavior that can't be changed.

After gathering DTMF tones, you have to transfer the call to the Vapi assistant using conference call.