The first sentence I see is: "When you cast this spell, you inscribe a glyph that later unleashes a magical effect." The Spell Glyph has to target a single creature or an area. Beyond that, fair game. You can have a stick you break to give yourself Stoneskin. I personally like it as an emergency shield - Tiny Hut when you smash a small charm. We've used that to take a long rest in the middle of an ambush...
I have seen some sites quite the spell as “casting a harmful effect” so I can see why people are thinking thst. But the book doesn’t mention it and I’ve never seen errata on it