I’d say some sort of caterpillar droppings. Any chance of a photo?

My sister says it’s poop.

Horn worms poop little black grenade looking things that land on the leaves around it. They’re evil eating machines. They love my tomatoes, tomatillos and peppers. This looks like what I’ve got as well. You have to catch them early in the morning before the sun sends them off hiding.

Agree with Crochetkim. Looks like Hornworm droppings. They are a pain and hard to find because they are so well camouflage. Look along the stems near where the tomato plant is being eaten. And look very closely.