Just like zabbix_get for zabbix agent:
/usr/local/zabbix/bin/zabbix_get -s 10.10.10.1 -p10050 -k system.uptime
zabbix_agent -t vm.memory.size[free]
That is not possible. Simple checks are performed either by the server or the proxy, and they do not provide a way to query for such items.
If you want to test on zabbix server side, using the zabbix user you can check by using
zabbix_get -s <host> -p <port:10050> -k <key>
If the command is not found install it with your package manager, eg: apt install zabbix-get
You can also get the command available on the agent, by launching this command on agent
zabbix_agentd -p