The user interface of a Simics module consists of three parts: its attributes, its interfaces, and the commands it adds to the Simics command-line interface. You should try to make the user interface of your model similar in style to that of existing Simics models.
Every model should have an info command, giving static information about the device, and a status command, that gives dynamic information. See the Simics Programming Guide for more information.
Look at the interfaces of similar devices to see what other commands may be useful, and try to use the same names for similar commands and parameters. Use existing API functionality where appropriate, rather than inventing your own.