Merfolk Observer 
Creature — Merfolk Rogue
$0.17 #29920 0.79 16.4 years
When this creature enters, look at the top card of target player's library.
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Cards similar to Merfolk Observer expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
Dewdrop Spy98%
$0.15↓#239840.00↓18.6 years↑
"When this creature enters, look at the top card of target player's library."
Rootwater Mystic88%
$0.13↓#278820.00↓28.2 years↑
": Look at the top card of target player's library."
: Look at the top card of target player's library."
Case the Joint84%
$0.14↓#17987↑0.09↓4.4 years↓
"Draw two cards, then look at the top card of each player's library."
Orcish Spy80%
$0.11↓#20613↑0.12↓31.8 years↑
"
: Look at the top three cards of target player's library."
: Look at the top three cards of target player's library."
Aven Windreader78%
$0.06↓#292920.06↓24.9 years↑
": Target player reveals the top card of their library."
: Target player reveals the top card of their library."
Field of Dreams76%
$140.63↑#17465↑0.47↓32.3 years↑
"Players play with the top card of their libraries revealed."
Wizened Snitches76%
$0.28↑#14590↑0.93↑20.9 years↑
"Players play with the top card of their libraries revealed."
Goblin Spy75%
$0.24↑#250160.44↓25.9 years↑
"Play with the top card of your library revealed."
Visions74%
$0.18↑#276120.58↓32.3 years↑
"Look at the top five cards of target player's library. You may then have that player shuffle that library."
Architects of Will73%
$0.29↑#20426↑0.07↓17.3 years
"When this creature enters, look at the top three cards of target player's library, then put them back in any order."
Wu Spy72%
$23.11↑#296540.13↓27.3 years↑
"When this creature enters, look at the top two cards of target player's library. Put one of them into their graveyard."
Draugr Thought-Thief70%
$0.10↓#240600.37↓5.6 years↓
"When this creature enters, look at the top card of target player's library. You may put that card into their graveyard."
Moonring Island70%
$0.46↑#11720↑0.09↓18.3 years↑
", : Look at the top card of target player's library. Activate only if you control two or more blue permanents."
, : Look at the top card of target player's library. Activate only if you control two or more blue permanents."