Is Clockwork Swarm legal in Standard, Modern, and Commander?

Clockwork Swarm is legal in: Legacy, Vintage, Commander, Pauper.

Clockwork Swarm

Q: What type of card is Clockwork Swarm?

Clockwork Swarm is an Artifact Creature — Insect. Its oracle text reads: "Clockwork Swarm enters with four +1/+0 counters on it.Clockwork Swarm can't be blocked by Walls.At end of combat, if Clockwork Swarm attacked or blocked this combat, remove a +1/+0 counter from it.{X}, {T}: Put up to X +1/+0 counters on Clockwork Swarm. This ability can't cause the total number of +1/+0 counters on Clockwork Swarm to be greater than four. Activate only during your upkeep."

Artifact Creature — Insect

Clockwork Swarm enters with four +1/+0 counters on it.<br>Clockwork Swarm can't be blocked by Walls.<br>At end of combat, if Clockwork Swarm attacked or blocked this combat, remove a +1/+0 counter from it.<br>, : Put up to X +1/+0 counters on Clockwork Swarm. This ability can't cause the total number of +1/+0 counters on Clockwork Swarm to be greater than four. Activate only during your upkeep.