How to update ContentType Label through API chaining?
OK, I got it! I had to think backwards:

$result = civicrm_api3('ContactType', 'get', array(
  'sequential' =&gt; 1,
  'name' =&gt; "Organization",
  'api.ContactType.create' =&gt; array('label' =&gt; "Entity", 'id' =&gt; "\$value.id"),
));