We’re excited to announce that the Design Metadata API has moved from beta to GA. If you’ve been experimenting with it, your apps can now be submitted for review and published once approved.
The Design Metadata API gives you quick access to key design information—title, page count, page dimensions, and duration. Perfect for when you need a quick snapshot of a design’s structure. 
Read the getDesignMetadata API reference
If you have suggestions for additional metadata you’d like to see exposed, feel free to drop a reply in the thread!