replyTo property
ReplyTo is the transport's reply target for this message: Slack's thread_ts, or the Telegram message id it arrived as. Send it back as the body's replyTo to answer in the SAME thread. Empty means the transport reported none — a top-level Slack message, and every Discord and Teams message, since neither carries one — and a reply then lands at the top level of the room.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? replyTo;