What you posted has a syntax error, but it makes no difference as you cannot pass HTTP headers via $.post().
Provided you're on jQuery version >= 1.5, switch to $.ajax() and pass the headers (docs) option. (If you're on an older version of jQuery, I will show you how to do it via the beforeSend option.)
$.ajax({
url: 'https://url.com',
type: 'post',
data: {
access_token: 'XXXXXXXXXXXXXXXXXXX'
},
headers: {
Header_Name_One: 'Header Value One', //If your header name has spaces or any other char not appropriate
"Header Name Two": 'Header Value Two' //for object property name, use quoted notation shown in second
},
dataType: 'json',
success: function (data) {
console.info(data);
}
});