Muzzio, Visionary Architect — ruling 1

The value of X is determined as the ability resolves. If, at that time, you control no artifacts, you won't look at any cards.

Muzzio, Visionary Architect : règles, fonctionnement et interactions (MTG)

Muzzio, Visionary Architect 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

, : Look at the top X cards of your library, where X is the greatest mana value among artifacts you control. You may put an artifact card from among them onto the battlefield. Put the rest on the bottom of your library in any order.

How it works : Muzzio, Visionary Architect

Original English text — Wizards of the Coast / Scryfall

#1May 29, 2014· Wizards of the Coast
The value of X is determined as the ability resolves. If, at that time, you control no artifacts, you won't look at any cards.
No other card is named in this ruling.