This option determines if the user can make use of Webmin's poweful RPC calls feature, which is designed to allow this system to be controlled by a script or other Webmin server via HTTP. Because the RPC feature does not respect any module grants or fine-grained access controls, this option should only be enabled for fully trusted `root`-equivalent users.

In addition, if the RPC calls only option is selected, the user will not be able to use the Webmin UI. This is useful for creating a separate login with a longer password for RPC purposes only, as two-factor authentication cannot be used when making RPC calls.