I updated Eclipse with the new SDK tools (rev. 23), but now when Eclipse starts I receive the error:
This Android SDK requires Android Developer Toolk
It works for me :)
If for some reason you installed an ADT preview and need to revert back to the current stable, you can't use the dialog to install "new" software since what you want is actually an older one. Instead do this:
On ADT-bundled Eclipse I had to first uninstall the ADT and then do a fresh install.
To remove the ADT plugin from Eclipse:
For me it helped to delete Android 4.4W which is also API 20 and might be a cause for the conflict. So only install Android 4.4W or Android L until they fix it.
And (again this might only be for me) it only works in Android Studio not in Eclipse ...
WARNING
There is now an update for ADT 23.0.1, but the Windows and Linux scripts are messed up, so wait with the upgrade!
You could check for example tools/proguard/bin/*.sh in http://dl.google.com/android/android-sdk_r23.0.1-windows.zip.
I did this to solve the same issue (in OS X):
Hope it helps.
I have done following to resolve an issue.
Go to http://developer.android.com/sdk/installing/installing-adt.html and download the latest ADT ZIP file (at the bottom of page).
Go to Eclipse → menu Help → About Eclipse → Installation details
Delete Android DDM, Android Development Tools, Hierarchy Viewer, Native Development Tools, TraceView, etc., 22.X version.
Menu Help* → Install New Software → Add → Archive → *Select the downloaded ZIP file in step 1.
Select all the latest version of all 23 which I have deleted in step 3 and accept the license agreement.
Restart Eclipse, and it fixes my issue.