You can access all iscst tool features (as long as you have the Intel SSD Datacenter Tool) installed on your ESXi host by going to the path /opt/intel/isdct/ , then execute ./isdct for running all types of commands. This tool is good, and will allow you to upgrade/check firmware version . Refer to the manual.
Also, remember that each intel ssd datacenter tool is built for specific firmware/driver versions, so for example if you install the latest isdct, this will have the latest available firmware software for your NVMe/SSD drives. Always check compatibility between firmware/driver and their respective isdct utility.
Cheers,
Mario