The real question, particularly because you are in Pasadena, is whether you have a buidling permit for that bath with the city of Pasadena. If you don't, that could be big trouble.
The city has a policy that when properties transfer title everything must be permitted in order to issue a certificate of occupancy, which the buyer needs to occupy the property and get their financing.
In the iTech MLS system you can list a 1/4 bath. Usually that means a sink/.
You can list it in the MLS... usually it is listed as a half bath if you are just talking about a toilet and a sink. It is important to make sure you disclose to a buyer that there are not permits if that is the case. You can petition the assessor's office to make a change to your property profile that reflects the half bath as well... we did this with a home recently. You can also try to get a permit retroactively if the work was done up to code. Let us know if you have any questions!