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 afcontinue="DAILY2001.jpg|557" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:BARREL BOLT.pdf" />
      <f ns="6" title="File:BRACKET MATRIX 2010.pdf" />
      <f ns="6" title="File:Buckle flat.jpg" />
      <f ns="6" title="File:Buckles.pdf" />
      <f ns="6" title="File:Child harness.jpg" />
      <f ns="6" title="File:Child harness.jpg" />
      <f ns="6" title="File:Child restraint anchor.pdf" />
      <f ns="6" title="File:Child restraint anchor.pdf" />
      <f ns="6" title="File:Child restraint anchor.pdf" />
      <f ns="6" title="File:Correct seat belt usage.pdf" />
    </allfileusages>
  </query>
</api>