I\'m making an alternative for the GUI stand-alone SDK Manager (it\'s gone on Android SDK 25), I\'ve found in Android Studio the required XMLs to retrieve packages.
You must do 2 separate work to done:
for example:
in C:\Program Files (x86)\Android\android-sdk\platforms\android-23 in my laptop there is file with source.properties name with following contents:
Pkg.Desc=Android SDK Platform 6.0
Pkg.UserSrc=false
Platform.Version=6.0
Platform.CodeName=
Pkg.Revision=3
AndroidVersion.ApiLevel=23
Layoutlib.Api=16
Layoutlib.Revision=3
Platform.MinToolsRev=22
there is source.properties file in every folder.
I hope this helps you ;)