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>
    <alltransclusions gatcontinue="Breadcrumb|2685" />
  </query-continue>
  <query>
    <pages>
      <page pageid="12" ns="0" title="2Pack Anatomy" />
      <page pageid="23" ns="0" title="About ADempiere" />
      <page pageid="24" ns="0" title="About ADempiere ja" />
      <page pageid="28" ns="0" title="Account Dialog" />
      <page pageid="29" ns="0" title="Account Info" />
      <page pageid="36" ns="0" title="Accounting Setup" />
      <page pageid="2521" ns="0" title="ADempiere Application Menu" />
      <page pageid="2574" ns="0" title="Adempiere Install for Windows &amp; PostgreSQL" />
      <page pageid="2628" ns="0" title="ADempiere Version Control" />
      <page pageid="2630" ns="0" title="ADempiere Virtual Appliance" />
    </pages>
  </query>
</api>