Stoic Rebuttal — ruling 1

Stoic Rebuttal’s metalcraft ability functions while Stoic Rebuttal is on the stack.

Stoic Rebuttal — ruling 2

For the purpose of determining whether the cost reduction applies, the number of artifacts you control is checked as you cast Stoic Rebuttal, before your last chance to activate mana abilities to pay for it. For example, if you control three artifacts, you could determine that Stoic Rebuttal costs {U}{U} to cast, then sacrifice one of those artifacts to activate a mana ability.

Stoic Rebuttal : règles, fonctionnement et interactions (MTG)

Stoic Rebuttal 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

Metalcraft — This spell costs less to cast if you control three or more artifacts. Counter target spell.

How it works : Stoic Rebuttal

Original English text — Wizards of the Coast / Scryfall

#1January 1, 2011· Wizards of the Coast
Stoic Rebuttal’s metalcraft ability functions while Stoic Rebuttal is on the stack.
No other card is named in this ruling.
#2January 1, 2011· Wizards of the Coast
For the purpose of determining whether the cost reduction applies, the number of artifacts you control is checked as you cast Stoic Rebuttal, before your last chance to activate mana abilities to pay for it. For example, if you control three artifacts, you could determine that Stoic Rebuttal costs to cast, then sacrifice one of those artifacts to activate a mana ability.
No other card is named in this ruling.