Since this tool is online based you don´t need any special requirements for your device. This online Clash of Kings hack generator is mobile optimized and should work well with most known devices. Yes, it is tested with different devices and browswers and should be bug-free. Some have said that the tool froze, but it helps to reload the page and all should be good again.
As for the game itself, it runs on multiple platforms - iOS and Android. Since these platforms are straight-forwards, this game is optimized to run on them. A little different topic is the PC version, which should be released any minute now. It has quite demanding parameters your desktop/laptop must have.