Ophidian 

Creature — Snake
Whenever this creature attacks and isn't blocked, you may draw a card. If you do, this creature assigns no combat damage this turn.
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Cards that do something similar 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.
Eternal of Harsh Truths 96%
$0.22#17420
"Whenever this creature attacks and isn't blocked, draw a card."
Werewolf Pack Leader 90%
$0.39#8342
"Whenever this creature attacks, if you attacked with creatures with total power 6 or greater this combat, draw a card."
Jon Irenicus, Shattered One 89%
$0.33#7523
"Whenever a creature you own but don't control attacks, you draw a card."
Gaea's Courser 85%
$0.04#24471
"Whenever this creature attacks, if there are three or more creature cards in your graveyard, draw a card."
Angelic Sell-Sword 85%
$0.44#8244
"Whenever this creature attacks, if its power is 6 or greater, draw a card."
Stromgald Spy 84%
$0.15#29721
"Whenever this creature attacks and isn't blocked, you may have defending player play with their hand revealed for as long as this creature remains on the battlefield. If you do, this creature assigns no combat damage this turn."
Isperia, Supreme Judge 84%
$0.31#9985
"Whenever a creature attacks you or a planeswalker you control, you may draw a card."
Ma Chao, Western Warrior 84%
$80.20#26861
"Whenever this card attacks alone, it can't be blocked this combat."
Cloak of Confusion 84%
#27647
"Whenever enchanted creature attacks and isn't blocked, you may have it assign no combat damage this turn. If you do, defending player discards a card at random."
Abyssal Nightstalker 84%
$0.50#27330
"Whenever this creature attacks and isn't blocked, defending player discards a card."
Historian of Zhalfir 83%
$0.07#30706
"Whenever this creature attacks, if you control a Teferi planeswalker, draw a card."
Jeskai Elder 83%
$0.16#18047
"Whenever this creature deals combat damage to a player, you may draw a card. If you do, discard a card."
Wharf Infiltrator 83%
$0.37#6458
"Whenever this creature deals combat damage to a player, you may draw a card. If you do, discard a card."
Daring Saboteur 83%
$0.23#10729
"Whenever this creature deals combat damage to a player, you may draw a card. If you do, discard a card."
Abomination of Gudul 83%
$0.05#27101
"Whenever this creature deals combat damage to a player, you may draw a card. If you do, discard a card."