Unique message ID assigned by the platform.
Platform this message came from.
Conversation/chat ID.
Conversation type.
Who sent the message.
Message content.
Raw text representation (convenience — extracted from content blocks).
ISO timestamp from the platform.
Optional replyMessage being replied to, if this is a reply.
Optional rawPlatform-specific raw data (for adapters that need pass-through).
Inbound message received from an external platform.