[TDO2000]

at the moment there is no way to use parameters with functions
the () are just used to say, that a function is called...
but functions in gscript accept every variable that was set in the NPC so u can just use this.test if u set it somewhere else in the whole code like

if(playerenters){
this.test=5;
showtext();
}

function showtext() {
message The Number is #v(this.test);
}