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="Blank_flexiviews.png|986" />
  </query-continue>
  <query>
    <pages>
      <page pageid="58" ns="0" title="Import from BIBID v1" />
      <page pageid="92" ns="0" title="IBID Referral" />
      <page pageid="146" ns="0" title="Missing Hospital Numbers from BIBID Import" />
      <page pageid="163" ns="10" title="Template:BIBID Import" />
      <page pageid="166" ns="0" title="About Patient Folders" />
      <page pageid="353" ns="0" title="Login to IBCS Author" />
    </pages>
  </query>
</api>