[Skript]

[TrainerX]

How do i detect the number of lines of lore a tool has? If I use 

set line 12 of lore of tool to "Fortune %{fortune.%player%}%"

then the textbox would appear very large

[Magician]

There is probably an expression for it but you can use a function such as:

function loreLength(i: item):: integer:
	set {_n} to 0
	while {_n} is set:
		if line ({_n} + 1}) of {_i}'s lore is set:
			add 1 to {_n}
		else:
 			exit loop
	return {_n}

Then using that function, you can do something along the lines of:

command /lorelength:
	trigger:
		set {_a} to loreLength(tool)
		send "This item has %{_a}% lines of lore."

I broke it down a little so it's easier to understand. Hopefully this helps. The indentation is kinda big but that's just how Minehut forums converts TABs.

[Migins]

If you can, it would be easier if you didn't use a function and just used it directly in the command. Functions (in skript) load considerably slower.