Idempotency

Repeating a request (because the network dropped, say) must never duplicate contacts, deals or messages.

Every POST accepts the Idempotency-Key header (1 to 255 characters). Always use it to send messages (POST /v1/conversations/{id}/messages); it is recommended on every POST.
The same key with the same body, within 24 hours, returns the same result without repeating the action.
The same key with another body, or while the first request is still running: 409 idempotency_conflict.
PUT /v1/contacts/by_identifier/{identifier} and PUT /v1/crm/deals/by_external_id/{external_id} are idempotent by design: no header needed.
In MCP, send_message takes an idempotency_key argument.

curl -X POST "https://atende.suporteja.com.br/v1/conversations/1543/messages" \
  -H "Authorization: Bearer $ATENDLLY_API_KEY" -H "Content-Type: application/json" \
  -H "Idempotency-Key: order-98765-shipped" \
  -d '{"content": "Your order 98765 was shipped."}'