Questions about Help Center API::Articles::Create Article

Hello everyone,

As you read the following, I am trying to create something in gas that will create articles in the Help Center.

It says that required fields are missing, but what is missing?

Referring URL
https://developer.zendesk.com/api-reference/help_center/help-center-api/articles/
See Create Article

Created program (gas)
*How to execute the API

function zendeskPostArticle() {

  var url = 'https://xxxxxxxxx.zendesk.com/api/v2/help_center/ja/sections/**********/articles';

  const TOKEN = '********';
  const EMAIL = '********';

  var postjson = {
    "article": {
      "body": "Use a tripod",
      "locale": "ja",
      "permission_group_id": ******,
      "title": "Taking photos in low light",
      "user_segment_id": *****
    },
    "notify_subscribers": false
  }

  var options = {
      'method': 'POST',
      'headers': {
          'Authorization': "Basic " + Utilities.base64Encode(Utilities.newBlob(EMAIL + '/token:' + TOKEN).getBytes()),
          'contentType': 'application/json',
          'Accept': 'application/json'
      },
      'payload': JSON.stringify(postjson)
  };

  var response = UrlFetchApp.fetch(url, options);
  var json = JSON.parse(response.getContentText("UTF-8"));
}

The error that occurred:

Exception: Request failed for https://xxxxxxxxx.zendesk.com returned code 400. Truncated server response: Required parameter missing: article

thank you