Hi all,
I just want to give a suggestion for all Extension’s Developers: To indicate, in your extensions, what is the minimum API Level that the extension can be used. It helps to determine which minimum API Level our app’s going to be.
In my case I use some extensions and I really don’t know the minimum API Level I can use with all of them. So, I think it will help every user.
I’ll brag a bit and tell everyone, that I have Android Minimum API Level detail in Details section about every product. So, I comply with this 
Hello, It shouldn’t really matter about API Level in extensions, Most of the library’s are supported by most compilers so unless it is a depreciated version for a certain API Level it should work across the board. Its similar with some Apps, Might be API Compliant but might not work on certain devices.
Your builder determines the final API Levels, But likewise when built, some devices handle the App threads differently than expected. Sometimes the Builder used affects the Extension function as well,
A lot to consider 
Well, I had a case here with some extensions, where even I indicated the API 16, my app does not work con phones with that API. Because of that I had suggested this. And we have to consider that the majority of extensions does not inform which APIs they work.
Lucky Nathan already adds this to his extension.