These section shows the available type for the mock object. Note: In all examples, it’s using en_US as a default locale. mock accepts an object with one or more key-value proprieties. On each propriety, the key is the name of your field and the value is an object containing 2 proprieties:
Key NameTypeRequired
typeString✔
paramsArray
See the example below: 
{
  "mock": {
    "first_name": {
      "type": "firstName"
    },
    "last_name": {
      "type": "lastName"
    },
    "user_code": {
      "type": "numerify",
      "params": [
        'user-####'
      ]
    }
  }
}
Will output 
{
    "first_name": "Alan",
    "last_name": "Hettinger",
    "user_code": "user-0859"
}