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"?>
    <alltransclusions gatcontinue="Category_handler|148" />
      <page pageid="27" ns="10" title="Template:Dead link" />
      <page pageid="28" ns="10" title="Template:Fix" />
      <page pageid="105" ns="10" title="Template:Verify source" />
      <page pageid="126" ns="10" title="Template:According to whom" />
      <page pageid="129" ns="10" title="Template:Attribution needed" />
      <page pageid="135" ns="10" title="Template:BLP sources section" />
      <page pageid="137" ns="10" title="Template:BLP unsourced section" />
      <page pageid="139" ns="10" title="Template:Better source" />
      <page pageid="142" ns="10" title="Template:By whom" />
      <page pageid="147" ns="10" title="Template:Check talk" />