Using either one of the wiki's example usages for anvil recipes results in this error message when the world loads (CraftTweaker v4.1.5, RockyCore v0.4.0). "/ct syntax" doesn't show any errors.

I have no issues loading my test scripts. I'm going to need your script file.

Nevermind, it works with MTLib. I didn't know there is a dependency.

Ya, both CrT and MTlib are dependencies but I have them marked as optional since I originally had more features planned for this mod. I'll probably change this.