Webservice to use

URL

library/sections/{section_id}/folder?parent={parent_directory_id}

RESPONSE

<MediaContainer size="50" totalSize="75" allowSync="1" art="/:/resources/movie-fanart.jpg" identifier="com.plexapp.plugins.library" librarySectionID="4" librarySectionTitle="Mes&#233;k" librarySectionUUID="9d394985-28db-4341-a8a2-6477140a7092" mediaTagPrefix="/system/bundle/media/flags/" mediaTagVersion="1507205980" offset="0" thumb="/:/resources/movie.png" title1="Mes&#233;k" title2="By Folder" viewGroup="movie" viewMode="65592">
<Directory key="/library/sections/4/folder?parent=618" title="Aladdin.1992.CUSTOM.HUN.BDRip.x264-DWP" />