Right now if you give show flow-accounting a bad argument, it will display something like this:
vyos@vyos-test-2# run show flow-accounting interface eth0 port 33r usage: flow_accounting_op.py [-h] --action {show,clear,restart} [--filter [{interface,host,ports,top} [{interface,host,ports,top} ...]]] [--interface INTERFACE] [--host HOST] [--ports PORTS] [--top TOP] flow_accounting_op.py: error: argument --ports: Invalid ports: 33r
Most people will never run the script by hand though, so information how to use it by hand is useless for them. None of our scripts do that, they just display the actual error and exit.
This one shouldn't be different.