Hi,
Valid values and other properties you are looking for are called meta-attributes.
You can also inspect these with PCD APIs, using IAttributeSet api.
See following link for explanation and examples:
http://help.sap.com/saphelp_nw73/helpdata/en/49/f98e39994a38d8e10000000a42189b/content.htm
Best Regards,
Tal