Whispersteel Dagger 
Artifact — Equipment
$0.32 #16233 0.27 6.1 years
Equipped creature gets +2/+0.
Whenever equipped creature deals combat damage to a player, you may cast a creature spell from that player's graveyard this turn, and you may spend mana as though it were mana of any color to cast that spell.
Equip 
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Cards similar to Whispersteel Dagger 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.
Scythe of the Wretched78%
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"Equipped creature gets +2/+2."
+2 more matching lines
Tinybones, the Pickpocket78%
$4.99↑#2557↑0.49↑2.5 years↓
"Whenever this card deals combat damage to a player, you may cast target nonland permanent card from that player's graveyard, and mana of any type can be spent to cast that spell."
Havengul Lich74%
$0.65↑#6074↑0.73↑14.7 years↑
"
: You may cast target creature card in a graveyard this turn. When you cast it this turn, this creature gains all activated abilities of that card until end of turn."
: You may cast target creature card in a graveyard this turn. When you cast it this turn, this creature gains all activated abilities of that card until end of turn."
Shadow of the Enemy70%
$1.05↑#10387↑0.84↑3.3 years↓
"Exile all creature cards from target player's graveyard. You may cast spells from among those cards for as long as they remain exiled, and mana of any type can be spent to cast them."