Sent when a tag is added to a contact — via the tag endpoints (POST /api/v1/contacts/{id}/tags), a contact create/update that includes tags, one event per tag added.
{
"event": "contact.tag_added",
"timestamp": "2026-07-06T14:24:18.321Z",
"data": {
"contact_id": "550e8400-e29b-41d4-a716-446655440000",
"email": "subscriber@example.com",
"tag": "vip"
}
}