About Pocket Judge
A deterministic rules engine for Magic: The Gathering — like having a judge in your pocket.
What Is Pocket Judge?
Pocket Judge is a free, community-driven rules engine built for Magic: The Gathering players of all levels. Whether you're resolving a complex board state at Friday Night Magic, settling a dispute during a Commander game, or studying for judge certification, Pocket Judge delivers fast, accurate rulings grounded in the official Comprehensive Rules — no guesswork, no AI hallucinations, just deterministic rules analysis.
Our engine analyzes over 35,000 cards from the complete Scryfall database, cross-referencing oracle text, card types, keyword abilities, and the full MTG Comprehensive Rules to resolve even the most intricate interactions. From layer conflicts and replacement effects to triggered ability timing and stack priority, Pocket Judge handles the rulings that trip up even experienced players.
But Pocket Judge is more than just a rules engine. It's a full-featured hub for the MTG community: host and join tournaments, build and share decks, discuss strategy in forums, and earn real cards through our monthly Developer Drawing.
What Makes Pocket Judge Different
Unlike chatbots and search engines that guess at answers, Pocket Judge uses a deterministic rules engine. Every ruling is produced by analyzing the actual game mechanics — triggered abilities, static effects, replacement effects, layer interactions, state-based actions, and priority rules — following the same logic a certified judge would apply at a tournament. Each response includes specific Comprehensive Rules citations so you can verify the ruling yourself.
The engine covers the full breadth of MTG mechanics including enters-the-battlefield triggers, dies triggers, cast triggers, combat interactions, stack timing, mana cost modifications, counter interactions, graveyard recursion, layer conflicts, protection and hexproof, and restriction and permission effects. Our test suite validates rulings across thousands of real-world card interactions to ensure accuracy.
Supported Formats and Interactions
Pocket Judge provides rules rulings that apply across all Magic: The Gathering formats — Standard, Modern, Legacy, Vintage, Pioneer, Commander (EDH), Pauper, and limited formats like Draft and Sealed. The Comprehensive Rules are format-agnostic, so the rulings you receive here are valid regardless of which format you play. The engine currently focuses on card interaction rulings and game mechanics rather than format-specific legality or ban list questions.
Rules Engine
Ask any rules question in plain English. The engine identifies cards, parses oracle text, and walks through the relevant rules interactions step by step with CR citations.
Tournaments
Create and manage tournaments with Swiss pairings, round timers, projector display mode, and live standings. Join events with a code or browse public tournaments.
Forums
Community discussion boards for rules questions, strategy, deck tech, and general MTG talk. Card names auto-link to images and oracle text.
Deck Builder
Build decks with instant card search, mana curve visualization, color breakdown, and format legality checks. Share decks publicly or keep them private. Includes a goldfish playtester.
Messages
Private messaging between players. Coordinate matches, discuss trades, or just chat. Unread badges keep you informed across the site.
Developer Drawing
Report incorrect rulings to earn entries into the monthly giveaway. Each validated bug report = one entry. Real Magic cards shipped to winners every month.
How the Rules Engine Works
When you ask a question, the engine runs it through a multi-stage pipeline. No neural networks, no probabilistic guessing — every decision is made by deterministic code that follows the Comprehensive Rules.
The handler pipeline includes specialized analyzers for every major rules area: color identity, layers and timestamps, replacement effects, triggered abilities, stack timing, state-based actions, protection, and more. For multi-card interactions, the Oracle Analyzer reads both cards' oracle text and explains the specific interaction with rule citations.
The engine is tested against a corpus of 13,012 questions spanning 86 categories. Every change is validated against this corpus to prevent regressions, and answers are manually spot-checked for quality. The current eval score is 97.4% with a 98.9% pass rate and a 0% crash rate.
Why No AI?
We tested LLM-based approaches (local Ollama models) during development. The results were clear: 6% outright incorrect rulings and a 10% hallucination rate. When a player asks "Does protection from red stop Blasphemous Act?", they need a correct answer, not a plausible-sounding one.
A deterministic engine can be audited, tested, and corrected. When it gets something wrong, we fix the underlying logic and it stays fixed. An LLM can give different answers to the same question depending on the day. For rules questions, reliability beats creativity every time.
Why We Built This
Magic: The Gathering has over 35,000 unique cards and a rulebook spanning hundreds of pages. Not every game store has a judge on hand, not every playgroup has a rules expert, and not every tournament has enough judges for every question.
Pocket Judge fills that gap — a fast, free, and accurate rules resource that any player can use, anytime, anywhere. We believe every player deserves a fair and correctly-ruled game, whether you're playing at a kitchen table or in a Grand Prix.