Send a WhatsApp template 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 approved WhatsApp template message to an existing contact (template-only; free-form session messages are not available through the public API). Requires the WhatsApp channel and honors the opt-out list.

POST /api/v1/whatsapp

Required scope: write:messages

Request body: JSON SendWhatsAppRequest

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