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

Minecraft Creator Tools command line and libraries.

{
  "format_version": "1.21.110",
  "minecraft:voxel_shape": {
    "description": {
      "identifier": "examplens:examplename"
    },
    "shape": {
      "boxes": [
        {
          "min": [0, 0, 0],
          "max": [16, 16, 16]
        }
      ]
    }
  }
}