---
title: "Register a message return line"
method: POST
path: "/v1/auth/sign-in/message-lines"
tags: ["Auth"]
---

# Register a message return line

`POST /v1/auth/sign-in/message-lines`

## Request

- Base URL: `https://api.configure.dev`
- URL: `https://api.configure.dev/v1/auth/sign-in/message-lines`
- Auth: API key in header `X-API-Key`

Registers the current provider-owned SMS/iMessage return line for the acting agent before that phone is used in message sign-in URLs. Configure stores only a hash and last4.

## Headers

- `X-Agent` string

## Request body

- MessageLineRegistrationRequest
  - `channel` string
  - `phone` string, required: Current provider-owned message return line in E.164 format.
  - `label` string, nullable
  - `metadata` object: Small server-side metadata object for provider bookkeeping.

## Response `201`

Message return line registered.

- MessageLineRegisterResponse
  - `line` MessageLine, required
    - `id` string, uuid, required
    - `channel` string, required
    - `phoneLast4` string, required: Last four digits of the registered line. Raw phone numbers are never returned.
    - `label` string, nullable, required
    - `status` 'active' | 'revoked', required
    - `createdAt` string, date-time
    - `updatedAt` string, date-time

## Other responses

- `400`: Request shape is invalid.
- `403`: Forbidden. Common causes include secret_key_required, token_wrong_type, approval_required, or access_denied.

---

[API](https://skmtc.dev/configure/apis/configure-http-api.md) · [All operations](https://skmtc.dev/configure/apis/configure-http-api/llms.txt) · [OpenAPI document](https://skmtc.dev/configure/apis/configure-http-api/revisions/ec760a9533d2?raw)