UX/UI at Rocket Internet Berlin
A simple rule: You should provide feedback whenever a permission is denied.
Permissions that are less clear should provide education about what the permission involves. If your app has a walkthrough, use it to explain what your app does and why unexpected permissions will be requested.
Apps should clarify why each permission request is needed, either through the feature name or an explanation provided. Remember, if you want to get a Yes answer, you have to ask nicely.