LTW3/data/minecraft/loot_tables/entities/mule.json

{
  "type": "minecraft:entity",
  "pools": [
    {
      "rolls": 1.0,
      "bonus_rolls": 0.0,
      "entries": [
        {
          "type": "minecraft:item",
          "functions": [
            {
              "function": "minecraft:set_count",
              "count": {
                "type": "minecraft:uniform",
                "min": 0.0,
                "max": 2.0
              },
              "add": false
            },
            {
              "function": "minecraft:looting_enchant",
              "count": {
                "type": "minecraft:uniform",
                "min": 0.0,
                "max": 1.0
              }
            }
          ],
          "name": "minecraft:leather"
        }
      ]
    }
  ]
}