Goblin Spymaster — ruling 1

If, during your declare attackers step, a creature you control is tapped or is affected by a spell or ability that says it can't attack, then it doesn't attack, even if you control one of Goblin Spymaster's tokens. If there's a cost associated with having a creature attack, you aren't forced to pay that cost, so it doesn't have to attack in that case either.

Goblin Spymaster : règles, fonctionnement et interactions (MTG)

Goblin Spymaster is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

First strike At the beginning of each opponent's end step, that player creates a 1/1 red Goblin creature token with "Creatures you control attack each combat if able."

How it works : Goblin Spymaster

Original English text — Wizards of the Coast / Scryfall

#1November 8, 2016· Wizards of the Coast
If, during your declare attackers step, a creature you control is tapped or is affected by a spell or ability that says it can't attack, then it doesn't attack, even if you control one of Goblin Spymaster's tokens. If there's a cost associated with having a creature attack, you aren't forced to pay that cost, so it doesn't have to attack in that case either.
Card named in this ruling
Goblin