The following is a JSON example for import with one custom object definition named Vehicle:

{
  "Vehicle": {
    "type": "Vehicle",
    "schema": {
      "object": "Vehicle",
      "label": "Vehicle",
      "title": "Vehicle",
      "type": "object",
      "description": "Object stores vehicle information",
      "enableCreateRecordAuditing": false,
      "enableDeleteRecordAuditing": false,
      "properties": {
        "brand__c": {
          "maxLength": 512,
          "description": "The brand of the vehicle",
          "label": "Brand",
          "type": "string"
        },
        "model__c": {
          "maxLength": 512,
          "description": "The model of the vehicle ",
          "label": "Model",
          "type": "string"
        },
        "color__c": {
          "maxLength": 512,
          "description": "The color of the vehicle",
          "label": "Color",
          "type": "string",
          "enum": [
                "white",
                "red",
                "black",
                "silver",
                "blue"
           ],
          "default": "white"
        },
        "MSRP__c": {
          "description": "The MSRP of the vehicle",
          "label": "MSRP",
          "type": "number"
        }
      },
      "required": [
        "brand__c",
        "model__c"
      ],
      "filterable": [
        "brand__c",
        "model__c"
      ],
      "enableRecordMigration": false
    }
  }
}