Conversational design seems like a brand new design discipline, however it's actually been around for a while. If you're creating conversational experiences, here is a partial list of lessons and wisdom to help your efforts.
Designing Voice User Interfaces
Wired for Speech: How Voice Activates and Advances the Human-Computer Relationship
So you want to be a voice designer
Voice UI Best Practices: Learning from Phone Systems
Designing for Actions on Google Assistant
Alexa Skills Kit Voice Design Guide
The Conversational UI and Why It Matters - Actions on Google
