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>
    <pages>
      <page pageid="62" ns="0" title="Barrel Calorimeter Commissioning" />
      <page pageid="209" ns="0" title="Checklist (HCO) maintenance Expert" />
      <page pageid="208" ns="0" title="Checklist maintenance (HCO) Expert" />
      <page pageid="231" ns="0" title="Dummy page 3" />
      <page pageid="228" ns="0" title="Fall 2016 GlueX Run" />
      <page pageid="36" ns="0" title="Solenoid Operations" />
      <page pageid="123" ns="0" title="Training and Safety" />
    </pages>
  </query>
</api>