---
title: "Start a Call Connect authentication session."
method: POST
path: "/call/start"
tags: ["call-connect-api"]
---

# Start a Call Connect authentication session.

`POST /call/start`

Start a Call Connect authentication session, triggering a user verification challenge based on the configured channels.

## Request body

- object
  - `referenceId` string, required — A reference identifier originating from customer experience/IVR system. This could be the call session ID.
  - `phoneNumber` string — The phone number of the user to be authenticated. This could be the current call's originating phone number. Either in a E.164 format, or optionally a local format as long as the `country` field is provided too. Required when using the SMS or WHATSAPP channel.
  - `userId` string — The primary identifier for the user stored in Authsignal.
  - `username` string — A username, for example a user customer number or email.
  - `email` string, email — An email address for the user to be authenticated.
  - `channel` 'WHATSAPP' | 'SMS' | 'EMAIL' — The channel to be used for the caller authentication link to be sent to the user.
  - `locale` string — The user's locale in BCP 47 format. Used to localize SMS messages.
  - `country` string — Optional - used if `phoneNumber` is provided in a non-E.164 format the country can be provided separately and Authsignal will automatically determine the E.164 formatted phone number.
  - `actionCode` string — The action code for the authentication session. Defaults to `call`.

## Response `200`

OK

- CallConnectSession
  - `messageId` string — The ID of the channel's delivered message, use this as an audit trail to track the message delivery.
  - `channel` 'WHATSAPP' | 'SMS' | 'EMAIL'
  - `email` string — The email address the authentication request was sent to. Present when the channel is EMAIL.
  - `phoneNumber` string — The phone number the authentication request was sent to. Present when the channel is SMS or WHATSAPP.

## Other responses

- `400` — Invalid Request
- `401` — Unauthorized

---

[API](https://skmtc.dev/authsignal/apis/call-connect-api.md) · [All operations](https://skmtc.dev/authsignal/apis/call-connect-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/authsignal/call-connect-api/revisions/5604d744e3ad/schema)