NSAppDataUsageDescription
A message that tells people why the app needs to access files in other apps’ sandbox containers.
Discussion
When your app tries to open a file that’s in another app’s sandbox container, the system requests permission from the person using the app and presents this message. If your app doesn’t have a value for the NSAppDataUsageDescription key in its information property list, the system presents a default message.
The system uses this message any time your app tries to access files in another app’s container, and your app can’t provide different messages for attempts to access containers from different apps.