darkwar123's post in Automatic market seller was marked as the answer
If somebody would be useful options need to look like this:
var options = {
url: 'https://steamcommunity.com/market/sellitem/',
headers: {
'Origin': 'http://steamcommunity.com',
'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.112 Safari/537.36',
'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8',
'Referer': 'http://steamcommunity.com/my/inventory/',
'Accept-Encoding': 'gzip, deflate',
'Accept-Language': 'ru,en-US;q=0.8,en;q=0.6,en-AU;q=0.4'
},
form: {
sessionid: this.sessionid,
appid: item.appid,
contextid: item.contextid,
assetid: item.assetid,
amount: 1,
price: item.price
}
};
