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>
    <allpages apcontinue="BGP_LS_PCEP:BGP" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="506" ns="0" title="BGP-LS/PCEP" />
      <p pageid="1341" ns="0" title="BGP-LS/PCEP:Helium Release Plan" />
      <p pageid="311" ns="0" title="BGP-LS/PCEP:Hydrogen Release Plan" />
      <p pageid="2137" ns="0" title="BGP-LS/PCEP:Lithium Release Plan" />
      <p pageid="894" ns="0" title="BGP-LS/PCEP:Release Notes 2013" />
      <p pageid="907" ns="0" title="BGP-LS/PCEP:Release Plan 2013" />
      <p pageid="1241" ns="0" title="BGP-LS/PCEP:User Guide HYDROGEN" />
      <p pageid="291" ns="0" title="BGP/PCEP protocol library" />
      <p pageid="290" ns="0" title="BGP/PCEP protocol library:Main" />
      <p pageid="4079" ns="0" title="BGP LS PCEP/FeatureTrees/Beryllium" />
    </allpages>
  </query>
</api>