Unshakable Tail

• WOTC Official Reminder Textofficial rules
  Surveil — Look at the top N cards of your library. Put any number of them into your graveyard and the rest on top of your library in any order.
• WOTC Official Reminder Textofficial rules
  Investigate — Create a Clue token. It's an artifact with ", Sacrifice this artifact: Draw a card."

• WWizards of the Coast2024-02-02
  Official Ruling
  You can't sacrifice a Clue to pay multiple costs. For example, you can't sacrifice a Clue token to activate its own ability and also to activate Alquist Proft, Master Sleuth's ability.
• WWizards of the Coast2024-02-02
  Official Ruling
  If an effect puts multiple cards from a library into a graveyard, all of those cards move at the same time. For example, when Aftermath Analyst's enters the battlefield triggered ability resolves, you'll mill three cards at once. If one or more of those cards are creature cards, Unshakable Tail's second ability will trigger.
• WWizards of the Coast2024-02-02
  Official Ruling
  Some spells and abilities that investigate may require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. You won't create any Clue tokens.
• WWizards of the Coast2024-02-02
  Official Ruling
  Some abilities trigger "whenever you sacrifice a Clue". Those abilities trigger whenever you sacrifice a Clue for any reason, not just to activate a Clue's activated ability.
• WWizards of the Coast2024-02-02
  Official Ruling
  If an effect refers to a Clue, it means any Clue artifact, not just a Clue artifact token. For example, you can sacrifice Wrench to pay for Alquist Proft, Master Sleuth's activated ability.
• WWizards of the Coast2024-02-02
  Official Ruling
  Clue is an artifact type. Even though it appears on some cards with other permanent types, it's never a creature type, a land type, or anything but an artifact type.

Rulings via Scryfall