To fix that, you have to open the SDK Manager, deselect the ‘Hide obsolete packages’ option on the bottom-right corner, and further, install the Android SDK Tools (obsolete) folder.

While Android Studio will normally let you know when you need to update something, you can also manage updates to the SDK manually via the manager. You’ll find this in Android Studio if you ...

You’ll find this in Android Studio if you navigate to Tools — Android — SDK Manager. You’ll see there are three tabs here for SDK Platforms, SDK Tools, and SDK Update Sites.