

Minions are fairly obviously weaker, when they are scaled to the party's level. If you give a similar description a session or two after describe the rules for minions (as you smartly plan to do), your players will get it, and more importantly their characters will have a reason have the same understanding. Most wield poorly made spears or rusty wood axes stolen from farmers.

You think there’s one in the back with a pot for a helmet. They seems smaller and definitely don’t have the sharpened swords or armor that the raiders had. These goblins don’t look like the raiding party you fought off outside of town on your way back from the temple. Looking out the spy hole you see dozens of them milling around, lighting buildings on fire, finishing off the few remain townsfolk who didn’t make it safely to the keep, and fighting over worthless trinkets. Only goblins cackle like this - there must have been some sort of raid in the hours you were hiding out from the Duke’s servants.

“As you approach the postern gate, glad to be free of the Duke’s generous “hospitality,” you begin to hear a cacophony of whooping and hollering. So in your horde of goblins example, I’d describe them as smaller or less well equipped than other goblins they’ve fought before: I try to describe the minions in a way that gives a clue that they are weaker using things that their characters would reasonably notice from experience.
