This post is from the WWDC26 App Intents & Siri Q&A.
Can I make functionality of my app available to Siri AI if they are NOT from one of the predefined App Schema domains? (This was already asked here: https://developer.apple.com/forums/thread/829586 ) Can I define my own App Schemas & App Schema Domains?
These questions were already answered here: https://developer.apple.com/forums/thread/831344