Trouble building tileset.json

General
1

I’m trying to build a tileset.json file by hand (in order to load two separate external tilesets) but the following json file is throwing an error in Cesium.
Weirdly enough, it I only use only one child, then there is no error.
The error is:

SyntaxError: Unexpected token } in JSON at position 730

Can someone suggest what I may be doing wrong?

{
  "asset": {
    "version": "1.0",
    "extras": {
      "ion": {
        "georeferenced": false,
        "movable": true
      }
    }
  },
  "geometricError": 50,
  "root": {
    "geometricError": 27,
    "boundingVolume": {
      "box": [
        0,
        0,
        11.406762820600573,
        10,
        0,
        0,
        0,
        5.564995514262032,
        0,
        0,
        0,
        11.406762820600573
      ]
    },
    "refine": "ADD",
    "children": [
      {
        "boundingVolume": {
          "box": [
            -5,
            0,
            11.406762820600573,
            5.158322987301894,
            0,
            0,
            0,
            5.564995514262032,
            0,
            0,
            0,
            11.406762820600573
          ]
        },
        "geometricError": 27,
        "content": {
          "uri": "3dtiles/tileset.json"
        },
      },
      {
        "boundingVolume": {
          "box": [
            5,
            0,
            11.406762820600573,
            5.158322987301894,
            0,
            0,
            0,
            5.564995514262032,
            0,
            0,
            0,
            11.406762820600573
          ]
        },
        "geometricError": 27,
        "content": {
          "uri": "3dtiles2/tileset.json"
        },
      }
    ]
  }
}
2

Pasting this in JSONLint (https://jsonlint.com/) shows where the issue is. You have an extra comma right here:

"geometricError": 27,
"content": {
	"uri": "3dtiles/tileset.json"
},

This is not officially maintained, but the 3d-tiles-validator repository does have an experimental “merge tilesets” script that describes the logic required to create a “parent” tileset.json that has two (or more) 3D Tilesets as children, combining the bounding volumes and geometric errors.