Siri is a virtual assistant that is part of Apple Inc.'s iOS, iPadOS, watchOS, macOS, tvOS and audioOS operating systems. The assistant uses voice queries and a natural-language user interface to answer questions, make recommendations, and perform actions by delegating requests to a set of Internet services.
Siri is the world’s most popular intelligent assistant. With Shortcuts and SiriKit, your apps can help users get things done using just their voice. iOS 13 makes things even more powerful with new conversational shortcuts, deeper customization, and new media playback experiences.
Design Guidelines https://developer.apple.com/siri/style-guide
Developer Guides https://developer.apple.com/documentation/sirikit
Help users quickly accomplish tasks related to your app with their voice or with a tap with the Shortcuts API. Siri intelligently pairs users’ daily routines with your apps to suggest convenient shortcuts right when they’re needed on the lock screen, in Search or from the Siri watch face.
Discussion Forum https://forums.developer.apple.com/welcome