@minecraft/creator-tools/data/content/newitemjson/feature_rule.json

Minecraft Creator Tools command line and libraries.

{
  "format_version": "1.21.70",
  "minecraft:feature_rules": {
    "description": {
      "identifier": "examplens:examplename"
    },
    "conditions": {},
    "distribution": {
      "iterations": 1,
      "x": 0,
      "y": 0,
      "z": 0
    }
  }
}