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On the "list of unsupported card groups" topic, I was listing these as unsupported:

Activated abilities that generate mana (Deathrite Shaman, Wall of Roots, Squandered Resources, Agent of Stromgald).

This has just been disproved, since Wall of Roots was added. I admit I was actually pretty unsure of what I was saying in this particular case.

What's the proper wording for this group of cards? I see now that the problem isn't related to being a mana ability or an activated ability. I think I remember melvin once said that the problem is that mana producing cards shouldn't have choices. Wall of Roots doesn't require any choices, while Shaman requires a target choice, Squandered requires choosing a land to sacrifice, and Agent the mana source to pay for the ability. Is that the key difference? I'd appreciate if someone could suggest a wording for this group.

Edit: Oh yeah, if anyone has spotted any other errors in that list, please do tell me. I'd rather not provide wrong information to people.

May be easier to state what is supported, which are activated mana abilities that can be activated at most once to pay for a single mana cost without any choices.

Deathrite Shaman's ability is not a mana ability as it has a target.

Squandered Resources's ability requires a choice and is repeatable (violates the at most once restriction).

Agent of Stromgald's ability requires a choice and is repeatable (violates the at most once restriction).

Putting a counter as in Wall of Roots is also repeatable, but the "at most once" requirement is restored by the activation condition "Activate this ability only once each turn"