{
  "processors": [
    {
      "processor_type": "minecraft:rule",
      "rules": [
        {
          "input_predicate": {
            "block": "minecraft:cobblestone",
            "predicate_type": "minecraft:random_block_match",
            "probability": 0.2
          },
          "location_predicate": {
            "predicate_type": "minecraft:always_true"
          },
          "output_state": {
            "Name": "minecraft:mossy_cobblestone"
          }
        }
      ]
    }
  ]
}