Send a text message to a contact who has opted in.

Base URL: https://api-admin-us-east.velaro.com/api/v1. Send your API key as Authorization: Bearer vlk_.... Create keys under Settings > API Keys; each key carries only the scopes you grant it.

Sends an SMS to an existing contact. Requires the SMS channel on the account and honors the site's phone opt-out list; opted-out numbers are refused with 422.

POST /api/v1/sms

Required scope: write:messages

Request body: JSON SendSmsRequest

Common responses: 401 for a missing or invalid key, 403 when the key lacks the scope, 429 when the rate limit is reached.