It is judgment, but there is specific guidance in MLBUM (and others):
5.1 PLAY OR ATTEMPTED PLAY
The following interpretation of "play or attempted play" applies to both awarding of bases
(Official Baseball Rule 7.05(g)) and appeal plays (Official Baseball Rule 7.10):
A play or attempted play is interpreted as a legitimate effort by a defensive player who has
possession of the ball to actually retire a runner. This may include an actual attempt to tag a
runner, a fielder running toward a base with the ball in an attempt to force or tag a runner, or
actually throwing to another defensive player in an attempt to retire a runner. (The fact that the
runner is not out is not relevant.) A fake or a feint to throw shall not be deemed a play or an
A play or attempted play:
(1) Runners on first and second, ground ball to the shortstop, who makes a swipe at the
runner from second but misses and then throws beyond first base into the stands.
Ruling: The swipe by the shortstop is an attempted play; thus the throw to first is not the
first play by an infielder (even though it is the first throw), and the proper award of bases
would be from the time of the throw.
(2) Runner on first and ground ball to second baseman who flips ball to short to get runner
from first but who is safe. Shortstop throws beyond first into the stands.
Ruling: The flip by the second baseman to the shortstop is an attempted play, even
though unsuccessful. The throw to first is not the first play by an infielder and thus runner
should be placed from the time of the throw. Runner who was on first would score and
batter-runner would be placed at second.
Not a play or attempted play:
(1) A fake or a feint to a base but not actually throwing, even though the fielder draws his
arm back to feint a throw.
(2) A pitcher feinting a throw toward a base to hold or check a runner's progress in order to
complete an appeal play at another base.
(3) Runner on first, ground ball to the shortstop, who starts to flip the ball to the second
baseman but does not and throws the ball beyond first and out of play.
Ruling: The feint to the second baseman is not considered a play or attempted play, and
award of bases is from the time of the pitch.
(4) Runners on first and third, runner on first stealing as ground ball is hit to shortstop. The
shortstop feints a throw home but does not throw-instead throws to first and into the
stands; during this time the runner from first has rounded second base.
Ruling: The feint by the shortstop toward home is not considered a play or attempted
play; thus the throw beyond first is the first play by an infielder and awards should be
made from the time of the pitch.