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

Clockwork Hydra is legal in: Modern, Legacy, Vintage, Commander.

Clockwork Hydra

Q: What type of card is Clockwork Hydra?

Clockwork Hydra is an Artifact Creature — Hydra. Its oracle text reads: "This creature enters with four +1/+1 counters on it. Whenever this creature attacks or blocks, remove a +1/+1 counter from it. If you do, it deals 1 damage to any target. {T}: Put a +1/+1 counter on this creature."