Version 2.5.0.0 was specifically tailored to handle then-current software like Windows 8.1 and Office 2013, bridging the gap before newer tools were developed for Windows 10.
If you are referring to the activation utility, it is important to note: Microsoft Toolkit 2.5.0.0
: It was never an official Microsoft product and using it violates the Windows End User License Agreement (EULA). Version 2
Modifying system-level licensing files can lead to unexpected crashes, broken Windows Updates, or the inability to upgrade to newer versions of the OS. broken Windows Updates