... and how to find it out (in an authorative way)?
In Android Studio 0.8.11: when I check the same it shows 10.0.8.11. which corresponds to http://tool
For newer Intellij versions (2020+): The build-in Android Gradle Plugin version is visible in Settings -> Plugins -> Android
: 10.android-version.intellijbuild-version
Example:
Source: https://youtrack.jetbrains.com/issue/IDEA-252823#focus=Comments-27-4444522.0-0