Correct syntax for command_state?

hello, would appreciate any advice - i am probably getting the syntax wrong here, but I can’t get the command_state to work.

I am using command line switches to send on / off triggers, from HA to a lighting server.
This works fine.
I would love to get state updates from the lighting server, but the command_state polling doesn’t work, here is my code:

platform: command_line
        friendly_name: "Home office wall lights"
        command_on: /usr/bin/curl -X POST ''
        command_off: /usr/bin/curl -X POST ''
        command_state: /usr/bin/curl -X POST ''

FYI the PHP script gives a 0 or a 1 for currently on or off respectively.
any ideas please?