If you mean the Your torch doesn’t have enough acetylene to cut that. message, it is hard coded in iuse.cpp and can not be changed via json. You need to either add a new use function, or change the existing function. Both solution require to recompile the game (and can not be distributed like a mod).
Btw. the function also mentions “Acetylene gas” when you chose the same square as the character to cut to, so you might want to change that as well.
Alternatively, you could write your use function in Lua (a scripting language), that script can be loaded and used just like json (without recompilation).