Aside from the narrative text, there isn't any way to document a description of an Organization (either a standard field or an extension). It may be valuable to convey context about the Organization in a way that's not comingled with a bunch of other free text version Organization content.

Location already has description and HealthcareService has comment.

We have already defined as an extension here:
http://build.fhir.org/ig/HL7/VhDir/StructureDefinition-org-description.html

This should be a core property.

See discussion here