The apiv3 does not return joined fields
Membership doesn't have a contact details(apart from id) in its API call. To get the address and display name, I think you need to call a chain API -

$result = civicrm_api3('Membership', 'get', array(
  'sequential' =&gt; 1,
  'api.Contact.get' =&gt; array('return' =&gt; "display_name, street_address"),
));


More about chaining - https://wiki.civicrm.org/confluence/display/CRMDOC/Chaining