Can we automate the unpleasantries in life instead of the pleasures?
I get the complaint, but how is this something that removes the human element at all?
The issue I see is that you'd need a huge amount of games to tell who's better (you need that between humans too, the game is very high variance.)
Another problem is that giving a positional evaluation to count mistakes is hard because MtG, in addition to having randomness, has private information. It could be rational for both players to believe they're currently winning even if they're both perfect bayesians. You'd need to have something that approximates "this is the probability of winning the game from this position, given all the information I have," which is almost certainly asymmetric and much more complicated than the equivalent for a game with randomness but not private information such as backgammon.
I'm not trying to compute a chess-style "player X was at 0.4 before this move and at 0.2 afterwards, so it was a -0.2 blunder", but I do have "blunder analysis" where I just ask Opus to second-guess every decision after the game is over - there's a bit more information on the Methodology page. So then you can compare models by looking at how often they blunder, rather than the binary win/loss data. If you look at individual games you can jump to the "blunders" on the timeline - most of the time I agree with Opus's analysis.
Once you get solid rankings for the different LLMs, I think a huge feature of a system like this would be to allow LLMs to pilot user decks to evaluate changes to the deck.
I'm guessing the costs of that would be pretty big, but if decent piloting is ever enabled by the cheaper models, it could be a huge change to how users evaluate their deck construction.
Especially for formats like Commander where cooperation and coordination amongst players can't be evaluated through pure simulation, and the singleton nature makes specific card changes very difficult to evaluate as testing requires many, many games.
The agents also constantly seem to evaluate if they're "behind" or "ahead" based on board state, which is a weird way of thinking about most games and often hard to evalaute, especially for decks like control which card more about resources like mana and card advantage, and always plan on stabalizing late game.
You can see the current prompt at https://github.com/GregorStocks/mage-bench/blob/master/puppe...:
"default": "You are a competitive Magic: The Gathering player. Your goal is to WIN the game. Play to maximize your win rate \u2014 make optimal strategic decisions, not flashy or entertaining ones. Think carefully about sequencing, card evaluation, and combat math.\n\nGAME LOOP - follow this exactly:\n1. Call pass_priority - this blocks until you have a decision to make, then returns your choices (response_type, choices, context, etc.)\n2. Read the choices, then call choose_action with your decision\n3. Go back to step 1\n\nCRITICAL RULES:\n- pass_priority returns your choices directly. Read them before calling choose_action.\n- When pass_priority shows playable cards, you should play them before passing. Only pass (answer=false) when you have nothing more you want to play this phase.\n\nUNDERSTANDING pass_priority OUTPUT:\n- All cards listed in response_type=select are confirmed castable with your current mana. The server pre-filters to only show cards you can legally play right now.\n- mana_pool shows your current floating mana (e.g. {\"R\": 2, \"W\": 1}).\n- untapped_lands shows how many untapped lands you control.\n- Cards with [Cast] are spells from your hand. Cards with [Activate] are abilities on permanents you control.\n\nMULLIGAN DECISIONS:\nWhen you see \"Mulligan\" in GAME_ASK, your_hand shows your current hand.\n- choose_action(answer=true) means YES MULLIGAN - throw away this hand and draw new cards\n- choose_action(answer=false) means NO KEEP - keep this hand and start playing\nThink carefully: answer=false means KEEP, answer=true means MULLIGAN.\n\nOBJECT IDs:\nEvery game object (cards in hand, permanents, stack items, graveyard/exile cards) has a short ID like \"p1\", \"p2\", etc. These IDs are stable \u2014 a card keeps its ID as it moves between zones. Use the id parameter in choose_action(id=\"p3\") instead of index when selecting objects. Use short IDs with get_oracle_text(object_id=\"p3\") and in mana_plan entries ({\"tap\":\"p3\"}).\n\nHOW ACTIONS WORK:\n- response_type=select: Cards listed are confirmed playable with your current mana. Play a card with choose_action(id=\"p3\"). Pass with choose_action(answer=false) only when you are done playing cards this phase.\n- response_type=boolean with no playable cards: Pass with choose_action(answer=false).\n- GAME_ASK (boolean): Answer true/false based on what's being asked.\n- GAME_CHOOSE_ABILITY (index): Pick an ability by index.\n- GAME_TARGET (index or id): Pick a target. If required=true, you must pick one.\n\nCOMBAT - ATTACKING:\nWhen you see combat_phase=\"declare_attackers\", use batch declaration:\n- choose_action(attackers=[\"p1\",\"p2\",\"p3\"]) declares multiple attackers at once and auto-confirms.\n- choose_action(attackers=[\"all\"]) declares all possible attackers.\n- To skip attacking, call choose_action(answer=false).\n\nCOMBAT - BLOCKING:\nWhen you see combat_phase=\"declare_blockers\", use batch declaration:\n- choose_action(blockers=[{\"id\":\"p5\",\"blocks\":\"p1\"},{\"id\":\"p6\",\"blocks\":\"p2\"}]) declares blockers and their assignments at once.\n- Use IDs from incoming_attackers for the \"blocks\" field.\n- To not block, call choose_action(answer=false).\n\nCHAT:\nUse send_chat_message to talk to your opponents during the game. React to big plays, comment on the board state, or just have fun. Check the recent_chat field in pass_priority results to see what others are saying."
"grudge-holder": { "name_part": "Grudge", "prompt_suffix": "You remember every card that wronged you. Take removal personally. Target whoever hurt you last. Keep a mental scoreboard of grievances. Forgive nothing. When a creature you liked dies, vow revenge." }, "teacher": { "name_part": "Teach", "prompt_suffix": "You explain your reasoning like you're coaching a newer player. Talk through sequencing decisions, threat evaluation, and common mistakes. Be patient and clear. Point out what the correct play is and why." },
Then they also see the documentation for the MCP tools: https://mage-bench.com/mcp-tools/. For now I've tried to keep that concise to avoid "too many MCP tools in context" issues - I expect that as solutions like tool search (https://www.anthropic.com/engineering/code-execution-with-mc...) become widespread I'll be able to add fancier tools for some models.
From the little I have seen they are different beasts (hidden information, number and complexity of rules...).
PS: Does this count as nerdsniping?
FOSS Magic clients are in a legal gray area at best. My mental model is that Wizards de facto tolerate clients like XMage and Forge because their UX is awful, but if you made something that's actually as user-friendly as MTGO/Arena, they'd sue you and you would lose.
Best to do this stuff in person I find.
I don't think there's a perfect way to do this, but I think trying to play 100 games with a deck and getting basic info like this would be super valuable.
You could clone mage-bench https://github.com/GregorStocks/mage-bench and add a new config like https://github.com/GregorStocks/mage-bench/blob/master/confi... pointing at the deck you want to test, and then do `make run CONFIG=my-config`. The logs will get dumped in ~/.mage-bench/logs and you can do analysis on them after the fact with Python or whatever. https://github.com/GregorStocks/mage-bench/tree/master/scrip... has various examples of varying quality levels.
You could also use LLMs, just passing a different `type` in the config file. But then you'd be spending real money for slower gameplay and probably-worse results.
https://github.com/spullara/mtg-reanimator
I have also tried evaluating LLMs for playing the game and have found them to be really terrible at it, even the SoTA ones. They would probably be a lot better inside an environment where the rules are enforced strictly like MTG Arena rather than them having to understand the rules and play correctly on their own. The 3rd LLM acting as judge helps but even it is wrong a lot of the time.
Of course when you quantize deck quality to such a degree I'd argue it's not fun anymore. YGO is already not fun anymore because of this rampant quantization and it didn't even take LLMs to arrive here.
This is also something I think the MTG community needs in many ways. I have been a relatively happy XMage user, although it has a bit to go, and before that was using GCCG which was great too!
The MTG community overall can benefit a lot from the game having a more entertaining competitive landscape, which has grown stale in many ways and Wizards has done a poor job since the Hasbro acquisition of doing much else besides shitting out product after product too fast with poor balance.
I have to imagine that Wizards is already running simulations, but they obviously aren't working well or they are choosing to disregard them. Hopefully it they are just had at doing simulations something like this can make it easier for them, and if not it will make the response time from the community better.
aethrum•1h ago
GregorStocks•1h ago
In practice they haven't really talked to each other, though. They've mostly just interpreted the prompts as "you should have a running monologue in chat". Not sure how much of this is issues with the harness vs the prompt, but I'm hoping to dig into it in the future.