Adding errors to form validation doesn't work?

Question

According to the Semantic UI docs on form validation, I can add errors manually:

add errors(errors) | Adds errors to form, given an array errors

Answer 1

To perform server-side validation via AJAX, use a custom rule:

$myForm = $('.ui.form');
var settings = {
    rules: {
        custom: function () {
            // Perform AJAX validation here
            return false;
        }
    }
};
var rules = {
    ajaxField: {
        identifier: 'ajaxField',
        rules: [{
            type: 'custom',
            prompt: 'Custom error!'
        }]
    }
};
$myForm.form(rules, settings);

Here it is in action: http://jsbin.com/sufiwafe/1/edit

For how to use callbacks and form validation in general, there is an important discussion on the Semantic-UI issues page on GitHub. The author mentions:

... the documentation was ambiguous but validation + settings is passed like $(".form').form(rules, settings);