operative

Adjective

• (of e.g. a machine) performing or capable of performing
  • in running (or working) order
    
  • a functional set of brakes
    

• effective; producing a desired effect
  • the operative word
    

• relating to or requiring or amenable to treatment by surgery especially as opposed to medicine
  • a surgical appendix
    
  • a surgical procedure
    
  • operative dentistry
    

• being in force or having or exerting force
  • operative regulations
    
  • the major tendencies operative in the American political system
    

Noun

• someone who can be employed as a detective to collect information

• a person secretly employed in espionage for a government

Related words

• Synonyms: 
  running(a) , functional , working(a) , surgical , private detective , PI , private eye , private investigator , shamus , sherlock , secret agent , intelligence officer , intelligence agent
• Antonyms: 
  medical , inoperative