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0027: Power and toughness ​

Status: Accepted. Amends decision 0026 (item 6).

Context ​

Decision 0026 left power and toughness changes unrecorded, relying on damage amounts to show their results. In the lasting-effects example, Tamiyo, Seasoned Scholar's trigger makes an attacking Ragavan a 1/1, but nothing in the file said so: a viewer could not show it, and a parser could not check that 1 damage was right. Tokens were worse: with no card behind them, a parser had no way to know their size at all.

MTGO reports each card's current power and toughness (the prototype recorder wrote "3/3" for Sowing Mycospawn), so recording them needs no rules engine in the writer.

Decision ​

  1. Power and toughness are recorded as state, not as effects: what they are, with the cause of each change, like life totals.
  2. A creature entering the battlefield carries pt PT on the line that puts it there, including creature tokens.
  3. Every change is a line OBJREF pt OLD -> NEW CAUSE straight after the event that caused it, whatever kind of effect caused it: spells and abilities, counters, static abilities starting or stopping, characteristic-defining abilities.
  4. A noncreature permanent's value is none; becoming or stopping being a creature is pt none -> 2/2 or pt 2/2 -> none. ? is used when the source does not report it.
  5. "Until end of turn" changes end with a line by rule:cleanup. A creature that leaves the battlefield needs no line.
  6. Keyframes give every creature's current pt.

Rules basis ​

Checked against the Comprehensive Rules effective 2026-09-25.

  • 208.1: "The first number is its power (the amount of damage it deals in combat); the second is its toughness".
  • 208.3: "A noncreature permanent has no power or toughness, even if it's a card with a power and toughness printed on it (such as a Vehicle)." Hence none.
  • 613.4: power and toughness come from several sublayers of effects (characteristic-defining abilities, setting effects, modifying effects and counters, switching). Recording the result avoids requiring writers to apply layers.
  • 122.1a: "A +X/+Y counter on a creature ... adds X to that object's power and Y to that object's toughness."
  • 604.3: characteristic-defining abilities, such as Tarmogoyf's, define power and toughness.
  • 514.2: in the cleanup step, "all 'until end of turn' and 'this turn' effects end."
  • 510.1a: "Each attacking creature and each blocking creature assigns combat damage equal to its power." Recorded power makes combat damage checkable.
  • 400.7: a creature that leaves the battlefield becomes a new object, so its modified power and toughness do not follow it.

Alternatives rejected ​

  • Recording every effect that changes power and toughness, as new effect lines. Rejected: writers would need to apply the layer system to know the result, and viewers would need it to display one. The result is what players see and what combat uses.
  • Leaving it to damage amounts (decision 0026 as first written). Rejected: unreadable mid-combat, uncheckable, and silent about tokens.
  • Recording only base power and toughness and letting parsers compute. Rejected: parsers would need every card's rules.

Consequences ​

  • Files are longer on turns with pump spells or anthems, by one line per creature affected.
  • Toughness and damage marked on creatures are visible, but marked damage itself is not yet recorded.
  • See examples/lasting-effects.mtgr and examples/more-situations.md.