Inbound message

Notification of an inbound message sent by a user to your WhatsApp Business number (`type: message`). The `message` object includes the content type (`text`, `image`, `video`, `document`, `audio`, `button`, `location`, `contacts`) and its data, along with the sender (`from`, `from_user_id`). The `context` field is only included when the message is a reply to a message you previously sent, and indicates the original `message_id` it replies to. For `contacts` messages (a user shares one or more contacts as vCards), `message.contacts` carries the shared contacts. Every field is optional — Meta omits the ones the user did not have in their address book — and any extra field Meta sends (e.g. `vcard`, `origin`) is propagated as-is: do not assume a closed shape.