Unfortunately what you are describing is not possible directly. NSCameraUsageDescription is a static string included in the Info.plist file and it's documented to require only one string (localized to multiple languages).

Apple's guideline in cases where more than one description is needed for different contexts is to use a custom pre-alert screen.

As @mehul-thakkar already pointed, try to generalize the string for NSCameraUsageDescription, but before displaying the system alert, show a custom screen or view that provides more context with one button that displays the system alert. You might want to make sure that this custom pre-alert screen is only displayed if permission is being requested for the first time.