minecraft-src/data/minecraft/loot_table/spawners/trial_chamber/key.json

{
  "type": "minecraft:chest",
  "pools": [
    {
      "bonus_rolls": 0.0,
      "entries": [
        {
          "type": "minecraft:item",
          "name": "minecraft:trial_key"
        }
      ],
      "rolls": 1.0
    }
  ],
  "random_sequence": "minecraft:spawners/trial_chamber/key"
}