Aven Courier — ruling 1

You choose the target permanent to put a counter on as you put the triggered ability of Aven Courier on the stack. You choose the kind of counter from a permanent as that ability resolves.

Aven Courier : règles, fonctionnement et interactions (MTG)

Aven Courier 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

Flying Whenever this creature attacks, choose a counter on a permanent you control. Put a counter of that kind on target permanent you control if it doesn't have a counter of that kind on it.

How it works : Aven Courier

Original English text — Wizards of the Coast / Scryfall

#1April 29, 2022· Wizards of the Coast
You choose the target permanent to put a counter on as you put the triggered ability of Aven Courier on the stack. You choose the kind of counter from a permanent as that ability resolves.
No other card is named in this ruling.