Start with the promise
People need to understand what the feature can do, what it needs from them and what remains their decision. Write that promise in plain language before designing the interaction.
Show the system working
Useful progress, sources and editable inputs build more confidence than an abstract loading animation. Choose the evidence that helps someone judge the result.
Design for correction
The most trustworthy intelligent products make revision easy. A person should be able to refine direction, undo a change and understand what will happen next.