NixOS-Config/modules/system/options/default.nix

{ lib, ... }:
with lib; {
  options = {
    system = {
      desktop.enable = mkOption {
        type = types.bool;
        default = true;
        description = "Enable desktop apps and services";
      };
      server.enable = mkOption {
        type = types.bool;
        default = false;
        description = "Enable server services";
      };
    };
  };
}