Microsoft has made the Volume Activation Management Tool to check license usage. For MAK (Multiple Activation Keys) you can view how many activations are remaining. Since we didn't want to start the tool every morning, I started debugging the application and made this thingy.
This tool requires python3, lxml and requests to function.
Standalone tool:
$ python3 mak.py product_key_id
Nagios check:
$ python3 check_mak.py product_key_id warning_limit critical_limit
define command {
command_name check-mak-remaining
command_line /usr/local/lib/nagios/plugins/check_mak.py $ARG1$ $ARG2$ $ARG3$
}