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>
    <allcategories>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">!Mensagens de aviso</c>
      <c size="3" pages="3" files="0" subcats="0" xml:space="preserve">!Predefinições de formatação</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">!Predefinições sobre física</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">%s</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">' .. cat .. '</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Administrador</c>
      <c size="20" pages="11" files="9" subcats="0" xml:space="preserve">Ajuda</c>
      <c size="5" pages="1" files="4" subcats="0" xml:space="preserve">Alex Nascimento de Mendonça</c>
      <c size="1" pages="0" files="1" subcats="0" xml:space="preserve">Ana Carolina Gonçalves de Almeida</c>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">Arthur Rosa Boni</c>
    </allcategories>
  </query>
  <query-continue>
    <allcategories accontinue="Astronomia" />
  </query-continue>
</api>