EXAMPLE: killed_by_player

{
    "pools": [
        {
            "rolls": 1,
            "entries": [
                {
                    "type": "item",
                    "name": "minecraft:stone",
                    "weight": 1,
                    "conditions": [
                        {
                            "condition": "killed_by_player"
                        }
                    ]
                }
            ]
        }
    ]
}