minecraft_lzstools/data/lzstools/predicate/unbreaking/offhand/all.json

{
  "condition": "minecraft:entity_properties",
  "entity": "this",
  "predicate": {
    "equipment": {
      "offhand": {
        "predicates": {
          "minecraft:enchantments": [
            {
              "enchantment": "minecraft:unbreaking",
              "levels": {
                "min": 1,
                "max": 3
              }
            }
          ]
        }
      }
    }
  }
}