Lupine Prototype 
Artifact Creature — Wolf Construct
This creature can't attack or block unless a player has no cards in hand.
click a line to search just that ability, click more to combine them
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.
Patchwork Beastie 94%
$0.25#12137
"This creature can't attack or block unless there are four or more card types among cards in your graveyard."
Relic Golem 94%
$0.19#8619
"This creature can't attack or block unless an opponent has eight or more cards in their graveyard."
Tiger-Dillo 94%
$0.07#22651
"This creature can't attack or block unless you control another creature with power 4 or greater."
Flowering Lumberknot 94%
$0.05#31116
"This creature can't attack or block unless it's paired with a creature with soulbond."
Wayward Swordtooth 90%
$4.18#986
"This creature can't attack or block unless you have the city's blessing."
Wirecat 88%
$0.28#31426
"This creature can't attack or block if an enchantment is on the battlefield."
Blind-Spot Giant 88%
$0.09#27137
"This creature can't attack or block unless you control another Giant."
Slumbering Dragon 81%
$2.40#12250
"This creature can't attack or block unless it has five or more +1/+1 counters on it."