Included package(custom Unity Tool that executing applications builds) in Package Manager by this guide: https://gist.github.com/LotteMakesStuff/6e02e0ea303030517a071a1c81eb016e I can see the package. Everything is working fine, except parts of the code that are using UnityEditor library(Getting errors about missing library) in my case it is executing a build of the application. Is it a bug or it should work this way? UPD: All editor functionality is working fine. I have an error only in the state of Building application.