Actually, it wasn’t enough. The index page is missing. I have solved it like this, unless there is a better way?
c::set('routes', array(
array(
'pattern' => 'uncss.json',
'action' => function() {
header('Content-type: application/json; charset=utf-8');
$pages = site()->index()->visible();
$root = site()->find('home');
$json = array();
$json[] = (string)$root->url();
foreach ($pages as $page) {
$json[] = (string)$page->url();
}
echo json_encode($json);
}
)
));
Well, thats lovely 
Congratulations. 