POST

Place AI Voice Call

Places an outbound AI voice call from an Agent to a contact.

POSThttps://api.vantaxai.com/v1/calls

The specified Agent dials out and, once the call connects, converses with the recipient in real time — answering questions, qualifying the lead, and booking appointments using its configured voice, knowledge base, calendar, and tools. Provide a `contact_id` to call a saved contact (recommended, so the call is attached to their timeline) or a raw `phone_number` for an ad-hoc dial. The call is placed asynchronously: this endpoint returns immediately with a `call_id` while the Agent rings and the call progresses through `ringing` → `in_progress` → `completed`. Poll Get Call or subscribe to the agent webhook for the final transcript, recording, and outcome.

Outbound consent

Contacts on the sub-account's Do-Not-Call list are rejected with a 409. Make sure you have consent to call before placing outbound campaigns.

Headers

Authorizationstringrequired
Bearer authentication with your secret API key.
example: Bearer vx_live_3fa9c2…
Content-Typestringrequired
Must be application/json for requests with a body.
example: application/json

Body Parameters

agent_idstringrequired
The Agent that will place and conduct the call.
example: agt_3d9b21
contact_idstringrequired
Contact to call. Required unless `phone_number` is supplied — provide one or the other.
example: ct_9d12fa
phone_numberstringoptional
E.164 number to dial when calling someone who isn't a saved contact. Used in place of `contact_id`.
example: +14155550188
from_phone_number_idstringoptional
Owned phone number to place the call from. Defaults to the Agent's assigned outbound number.
example: pn_55ad12

Request

curl -X POST https://api.vantaxai.com/v1/calls \
  -H "Authorization: Bearer vx_live_3fa9c2..." \
  -H "Content-Type: application/json" \
  -d '{
    "agent_id": "agt_3d9b21",
    "contact_id": "ct_9d12fa",
    "from_phone_number_id": "pn_55ad12"
  }'

const res = await fetch("https://api.vantaxai.com/v1/calls", {
  method: "POST",
  headers: {
    Authorization: "Bearer vx_live_3fa9c2...",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    agent_id: "agt_3d9b21",
    contact_id: "ct_9d12fa",
    from_phone_number_id: "pn_55ad12",
  }),
});
const { data: call } = await res.json();

const call = await vantax.calls.place({
  agentId: "agt_3d9b21",
  contactId: "ct_9d12fa",
  fromPhoneNumberId: "pn_55ad12",
});

call = vantax.calls.place(
    agent_id="agt_3d9b21",
    contact_id="ct_9d12fa",
    from_phone_number_id="pn_55ad12",
)

Response

{
  "success": true,
  "message": "Outbound call initiated",
  "data": {
    "id": "call_2b81e004",
    "sub_account_id": "sub_8a1f4c2e",
    "agent_id": "agt_3d9b21",
    "contact_id": "ct_9d12fa",
    "direction": "outbound",
    "status": "initiated",
    "from": "+18885550199",
    "to": "+14155550188",
    "created_at": "2026-06-10T12:00:00Z"
  }
}

{
  "success": false,
  "message": "Validation failed",
  "errors": [
    { "field": "contact_id", "message": "Provide either contact_id or phone_number" }
  ]
}

{
  "success": false,
  "message": "Contact is on the Do-Not-Call list",
  "code": "dnc_blocked"
}