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"?>
    <allfileusages gafcontinue="Baboon1.jpg" />
      <page ns="6" title="File:B52.climbout.arp.jpg" missing="" />
      <page ns="6" title="File:Babasteve-three boys.jpg" missing="" />
      <page pageid="100033343" ns="6" title="File:B17-G.jpg" />
      <page pageid="100112208" ns="6" title="File:B-25 in flight.JPG" />
      <page pageid="100112204" ns="6" title="File:B25s waiting to take off on Doolittle Raid.jpg" />
      <page pageid="100111089" ns="6" title="File:B-26.jpg" />
      <page pageid="100033350" ns="6" title="File:B29.jpg" />
      <page pageid="100159244" ns="6" title="File:B-52 being refueled.jpg" />
      <page pageid="100075784" ns="6" title="File:B52 carpet.jpg" />
      <page pageid="100159243" ns="6" title="File:B52 LITENING closeup.jpg" />