It's possible as you submit your app you are returned with an error requiring a camera description:
We have discovered one or more issues with your recent delivery for "Your App". To process your delivery, the following issues must be corrected:
This app attempts to access privacy-sensitive data without a usage description. The app's Info.plist must contain an NSCameraUsageDescription key with a string value explaining to the user how the app uses this data.
Once these issues have been corrected, you can then redeliver the corrected binary.
Carnival uses the camera in Video Call messages and a new validation for the submission process is requiring a description for the camera.
If you don't use these types of in app messages, your user will not see the dialog (it's shown only the first time you use the camera). Therefore, the text you put there is reasonably unimportant as it'll never be seen. We suggest something like: "We'd like to use the camera to show your face during Video Call based messaging."