operative

A person secretly employed in espionage for a government.

Someone who can be employed as a detective to collect information.

Relating to or requiring or amenable to treatment by surgery especially as opposed to medicine.

“operative dentistry”

(of e.g. a machine) performing or capable of performing.

Being in force or having or exerting force.

“operative regulations”

“the major tendencies operative in the American political system”

Effective; producing a desired effect.

“the operative word”