Style Guide
Specs & Assets: We’re using tools like InVision’s Inspect or Zeplin, nicely integrated with Sketch so it’s not necessary to waste any time redlining the designs with specs and measurements. Both tools have the ability to open a dialogue between the designer and developers so they can easily clarify any misalignments.
Mockups / Pages
A list of all the pages and use cases that will be used as references by developers. Most of those pages will be shown in the theme demo preview.
Interactions
Checklist
A Guide to Successful Design Handoffs 
Other resources:
Facilitating an Effective Design Studio