last_updated field indicates last update of the file and last_accessed indicates last activity in the file (e. g. submitting a suggestion). If there were no activities such as last_build, last_activity or last_updated, the dates is shown in following format 0000-00-00 00:00:00.
Unsuccessful response sample:
<?xml version="1.0" encoding="ISO-8859-1"?>
3API key is not valid