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
I faced the same problem and solved it. You need to uninstall the Android plugin entirely from within Eclipse (from the "about" section..), including trace view..
Then added the ADT Plugin again (https://dl-ssl.google.com/android/eclipse/) and install it.
The problem is solved!
I guess it's a bug with the SDK manager or ADT Plugin update mechanism...