You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="Rose.footer.gif" />
  </query-continue>
  <query>
    <pages>
      <page ns="6" title="File:Dark blue left arrow.svg" missing="" />
      <page ns="6" title="File:Dark blue right arrow.svg" missing="" />
      <page ns="6" title="File:Edit-copy green.svg" missing="" />
      <page ns="6" title="File:Imbox content.png" missing="" />
      <page ns="6" title="File:Imbox notice.png" missing="" />
      <page ns="6" title="File:Lua-logo-nolabel.svg" missing="" />
      <page ns="6" title="File:Redirect arrow without text.svg" missing="" />
      <page ns="6" title="File:Redirectltr.png" missing="" />
      <page pageid="93" ns="6" title="File:Oae.arms.gif" />
      <page pageid="153" ns="6" title="File:Oae.collar.gif" />
    </pages>
  </query>
</api>