This has been the case for quite a while. Like Reminders - You can't replace the phrase "Siri, remind me to ___" with a third party app. I'm surprised the EU lets them ship Reminders there.
That’s changing this year. They specifically demoed “send a message” and it went through their sample app, but there’s a schema for Reminders.
“Make your reminder app’s actions available to Apple Intelligence and Siri by adopting schemas for common reminder actions.”
https://developer.apple.com/documentation/appintents/app-sch...
https://developer.apple.com/videos/play/wwdc2026/240
That’s changing this year. They specifically demoed “send a message” and it went through their sample app, but there’s a schema for Reminders.
“Make your reminder app’s actions available to Apple Intelligence and Siri by adopting schemas for common reminder actions.”
https://developer.apple.com/documentation/appintents/app-sch...
https://developer.apple.com/videos/play/wwdc2026/240