agent vs agential

agent is a noun but agential is not a noun.

Word	Noun	Adjective	Verb	Adverb
agent	Yes	No	No	No
agential	No	Yes	No	No

agent (noun)	agential (noun)
the semantic role of the animate entity that instigates or causes the happening denoted by the verb in the clause
an active and efficient cause; capable of producing a certain effect
a businessman who buys or sells for another in exchange for a commission
a representative who acts on behalf of other persons or organizations
any agent or representative of a federal agency or bureau
a substance that exerts some force or effect

agent (adjective)	agential (adjective)
	of or relating to an agent or agency