Adding Validation to a WordPress Creation Toolkit Field

So I ran into a need to validate an email address for a frontend posting of a custom post type using Cozmos Labs WordPress Creation Toolkit.  Here is the code that I used to be able to accomplish that.  There is some commented out code that allows for you to see what is being passed in the field and values variables.

add_filter('wck_extra_message', 'wckc_text_as_email', 10, 6);
function wckc_text_as_email($message, $field, $required_fields, $meta, $values, $id) 
{ 
   if ($field[0]['slug'] == 'email') { 
      if(!filter_var($values['email'], FILTER_VALIDATE_EMAIL)) 
         return 'Please enter a valid Email Address !'; 
   } 
}