Every delivery is a POST with JSON body: 
{
  "eventId": "2915e81c-5068-4796-ace2-21d2c94ad298",
  "type": "message.received",
  "platform": "imessage",
  "projectId": "proj_…",
  "receivedAt": "2026-07-02T18:04:11.512Z",
  "data": { }
}

​
Event types

TypeWhen
message.receivedInbound message from a user
message.sentOutbound message confirmed
message.updatedMessage edited
message.failedSend failed
reaction.addedTapback or emoji reaction
reaction.removedReaction removed
typing.startedTyping indicator on
typing.stoppedTyping indicator off
readRead receipt
group.updatedGroup name, participants, or icon changed

​
Message payload

interface SkylineMessageEvent {
  id: string;
  channelId: string;
  from: string | null;
  text: string;
  fromMe: boolean;
  isGroup: boolean;
  replyTo: string | null;
  service: "imessage" | "sms" | "whatsapp";
  timestamp: string;
  attachments: Array<{
    id: string;
    name: string | null;
    mimeType: string | null;
    size: number | null;
  }>;
}
Attachments carry metadata only — never raw bytes. Fetch content on demand through the attachment API when needed.

​
Headers

HeaderDescription
x-interactions-signatureHMAC signature of the raw body
x-interactions-timestampUnix timestamp used in the signature