We might ascribe properties to a system but the utility is, does it help explain how a thing works. The name of the game is to communicate BDI from one agent to another. In XML terms you need something like RDF to say more about the tokens. KIF provides first order logic with set theory. Was intended as an Esperanto.
Ontology is common vocabulary.
Ontolingua was based on KIF and provided tools for defining collections of related terms. KQML is independent of transport, ontology and higher level protocols like contract net or auction. Most of the parameters are in every kind of performantive message. Not all agents understand all the commands. A question results in an error, refusal, an answer, or a deferral.