Why is my advancement not registering?

I'm trying to make an advancement that rewards the player with a function when they eat an apple, but after putting the text below in pack/advancement/food/apple.json (made with the help of misode.github.io) it refuses to even show up in the advancement registry. That means it's malformed in some way, but I can't for the life of me figure out what I've done wrong here.
It might change something that there's one of these for each food item, but I'm not sure.
{
  "criteria": {
    "eat": {
      "trigger": "minecraft:consume_item",
      "conditions": {
        "item": {
          "items": "minecraft:apple"
        }
      }
    }
  },
  "requirements": [],
  "rewards": {
    "function": "pack:food/apple"
  }
}