Urza

Commander brewing capapp for Magic: The Gathering — a workflow layer over j4th/mtg-mcp-server that adds collection-aware suggestions, stateful deck sessions, and pairwise interaction-density scoring.

What it is: an MCP server that extends j4th with four new capabilities:

1. Collection-aware brewing — ingest a Moxfield, Archidekt, or ManaBox CSV export, then get suggestions that boost cards you already own.
2. Pairwise interaction density — score every card pair for provides/needs overlap via Scryfall types + Commander Spellbook combo graph. Tribal decks land around 0.5 per pair, combo decks 1.5+, goodstuff piles ~0.1. Novel signal for brewing.
3. Stateful Commander deck sessions — create, add, remove, validate, and export decks across calls. More natural than passing the full list to every stateless tool.
4. Composite brew orchestrator — one call chains EDHREC staples + Spellbook combos + your collection + synergy density into a ranked suggestion list with rationale strings.

What it is not: a replacement for j4th. Urza mounts j4th underneath and inherits all 69 of its tools. Card search, combo lookup, draft analytics, rules engine, and metagame data all flow through unchanged.

Quick start

git clone https://github.com/<your-user>/urza.git
cd urza
uv sync
uv run urza

Claude Desktop / Claude Code config

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (Desktop) or ~/.mcp.json (Code):

{
  "mcpServers": {
    "urza": {
      "command": "uv",
      "args": ["--directory", "/absolute/path/to/urza", "run", "urza"]
    }
  }
}

Restart the client. You should see 88 tools — 69 from j4th + 19 Urza-specific, all prefixed urza_*.

Urza tools

Collection

Tool	Purpose
urza_collection_load	Load from a CSV file path
urza_collection_paste	Load from an inline paste
urza_collection_stats	Unique/total/top sets
urza_collection_only_owned	Filter a candidate list to owned cards
urza_collection_clear	Reset

CSV formats auto-detected: Moxfield, Archidekt, ManaBox. Double-faced cards match on the front face (case-insensitive).

Sessions

Tool	Purpose
urza_session_create	New Commander session (commander + optional partner/background)
urza_session_list	Summary of all sessions
urza_session_get	Full session state
urza_session_add	Add cards (list of {name, count})
urza_session_remove	Remove cards
urza_session_delete	Drop a session
urza_session_validate	Structural check (total == 100, singleton, basic-land bypass)
urza_session_export	Emit a Moxfield-format decklist

v0.1 validation is structural only — full color-identity and format-legality checks are deferred to v0.2.

Synergy

Tool	Purpose
urza_synergy_score	Pure math on a list of typed CardSignature objects
urza_synergy_build_graph	Build signatures from Scryfall bulk data + Spellbook combos
urza_synergy_analyze	One-shot: build graph + compute density

The math: for each card pair, count overlap across three channels — payoff (other needs what I provide), enabler (I need what other provides), trait (shared types/subtypes). Each overlap caps at 1 per pair. Weights: 8 / 8 / 0.5. Ported from the r2-d2 SWU capapp; see src/urza/synergy.py for the formula.

Brew

Tool	Purpose
urza_brew_suggest	Ranked suggestions. Chains EDHREC + Spellbook + collection + synergy. Optional session_id to score against an existing deck.
urza_brew_evaluate	Score a single candidate card against a commander (or session).

Composite score: synergy + edhrec_inclusion/5 + edhrec_synergy * 10 + (5 if owned). Rationale strings flag which factors dominated.

Architecture

Claude client (Desktop / Code / any MCP client)
        │
        │ stdio
        ▼
┌───────────────────────────────┐
│ Urza (FastMCP, 88 tools)      │
│                               │
│  urza_collection_*            │
│  urza_session_*               │
│  urza_synergy_*               │
│  urza_brew_*                  │
│                               │
│  ┌─────────────────────────┐  │
│  │ mounts j4th/mtg-mcp-    │  │
│  │ server — 69 tools:      │  │
│  │ scryfall_*, spellbook_*,│  │
│  │ edhrec_*, moxfield_*,   │  │
│  │ draft_*, goldfish_*,    │  │
│  │ spicerack_*, bulk_*,    │  │
│  │ plus workflow tools     │  │
│  └─────────────────────────┘  │
└───────────────────────────────┘
        │
        ▼
  Scryfall, Commander Spellbook, EDHREC, 17Lands,
  Moxfield, MTGGoldfish, Spicerack — via j4th

Urza depends on mtg-mcp-server >= 3.0.0 as a library and mounts its FastMCP instance. Upstream fixes in j4th flow to Urza users without a fork.

Development

uv sync
uv run pytest          # unit tests
uv run urza            # start stdio server

Pure-math tests cover synergy scoring and collection CSV parsing. Graph builder and brew tools are verified by end-to-end live tests against Scryfall + Spellbook + EDHREC (not included in the default test run; run manually).

Attribution

Urza is built on data from multiple sources, each with their own usage terms:

• Scryfall — card data via j4th's Scryfall adapter. Don't paywall Scryfall data; attribute back to Scryfall where displayed.
• Commander Spellbook — combo graph. MIT-licensed backend.
• EDHREC — commander staples and synergy signals. Undocumented JSON endpoints; cached aggressively and behind a feature flag in j4th.
• j4th/mtg-mcp-server by Justin Forth — the foundation. MIT-licensed. 69 tools across 8 backends.

Urza itself provides the brewing workflow layer (collection, sessions, synergy density, brew orchestration); all underlying data access is j4th's. If you find Urza useful, star j4th too.

License

MIT. See LICENSE.