How to make an enchantment show in the enchanting table

I am trying to make a custom enchantment but for some reason it doesn't seem to show up in the enchanting table, I tried with a weight of 200 and a min cost of 1 and it didn't drop so I assume it comes from the primary_items, but it is just "primary_items": "#minecraft:enchantable/leg_armor" so I don't see what is the issue. There is not always a primary_items field in the vanilla enchantments in the files of the game so I'm not sure of how it is supposed to be filled