Is Serene Sleuth legal in Standard, Modern, and Commander?

Serene Sleuth is legal in: Legacy, Vintage, Commander.

What type of card is Serene Sleuth?

Serene Sleuth is a Creature — Human Detective. Its oracle text reads: "When this creature enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") At the beginning of combat on your turn, investigate for each goaded creature you control. Then each creature you control is no longer goaded."