Google App Script with Twitter API (error 415)

[Alvesinho]

Hello, I am trying to code on google app script a program which allows to send a private message.

I can tweet but I can’t send a private message and twitter is giving me a 415 error.

But I find it strange because I can use the API to tweet.

Thank you in advance.

function run() {
  var service = getService();
  if (service.hasAccess()) {
    var url = 'https://api.twitter.com/1.1/direct_messages/events/new.json';
    var payload = {
      "event": {
        "type": "message_create",
        "message_create": {
          "target": {
            "recipient_id": "********************",
          },
          "message_data": {
            "text": "Hello world!",
          }
        }
      }
    };
    var response = service.fetch(url, {
      method: 'post',
      payload: payload,
      ContentType : "application/json"
    });
    var result = JSON.parse(response.getContentText());
    Logger.log(JSON.stringify(result, null, 2));
  } else {
    var authorizationUrl = service.authorize();
    Logger.log('Open the following URL and re-run the script: %s',
        authorizationUrl);
  }
} 

Here is the error indicated.