Create Topic from Google App Script

I’d like to create topics from a Google spreadsheet using Google App Script. My code looks like this, but I get a error message (400) when I run it:

function publishspeaker() {

var url = "";
var options = {
"method": "post",
"headers": {
"Content-Type": "multipart/form-data",
"Api-Username": "XXX",
"Api-Key": "Here_is_the_API_Key" 
"payload": {
"title": "This is a test",
"raw": "This is a test",
"category": 63
var response = UrlFetchApp.fetch(url, options);

Apparently, the category is invalid, but I don’t know why:

{“errors”:[“Du hast bei der Anfrage ungültige Parameter angegeben: category”],“error_type”:“invalid_parameters”}

Any ideas? Thanks!