Please read passed-named-or-query-string-params.
You should use query strings in CakePHP2.x Those are the correct form of passing values between urls via GET. They also play nicely with extensions.
Also, your action name is wrong. You should separate it into "action" and "ext":
array(
'controller' => 'posts',
'action' => 'points',
'ext' => 'json',
'?' => array('param1' => 1, ...)
),