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="Bazaar_items.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="846" ns="6" title="File:Battle report.png" />
      <page pageid="849" ns="6" title="File:Battle report attacker.png" />
      <page pageid="845" ns="6" title="File:Battle report defeat.png" />
      <page pageid="851" ns="6" title="File:Battle report defender.png" />
      <page pageid="847" ns="6" title="File:Battle report header.png" />
      <page pageid="852" ns="6" title="File:Battle report ingredients.png" />
      <page pageid="843" ns="6" title="File:Battle report message.png" />
      <page pageid="850" ns="6" title="File:Battle report resources.png" />
      <page pageid="848" ns="6" title="File:Battle report victory.png" />
      <page pageid="764" ns="6" title="File:Bazaar Dragon Eggs.png" />
    </pages>
  </query>
</api>