In most cases, you do not need an additional valve key. The Clik Valve has a knurled surface, which usually makes it easy to screw on and unscrew by hand.
A valve key is already included with the CLIK TEC conversion kits. This can be helpful if the valve is ever seated more tightly.
Another advantage: unlike conventional valves, the Clik Valve no longer requires you to screw a valve cap on or off. This makes it much less likely that the valve will accidentally loosen and need to be tightened again.