The building block of descript is the action. Every values the mod can use are actions, even fps and bps (blocks per second)
$attack return the value, so
{$attack} CPS
Return "? CPS"
But we can modify its return value using :
true means pressed
false means unpressed
{$attack:
true=[text:"key is pressed"; textColor:"ffffff"; backgroundColor:"ffffff"];
false=[text:"key is not pressed"; textColor:"ffff00"; backgroundColor:"ff00ff"]
}