Commander Workshop MCP

Commander Workshop is a local-first MCP server for building, checking, comparing, and fulfilling Magic: The Gathering Commander decks. It combines pinned rules and card data with your explicitly imported collection, keeps deck intent separate from ownership, and turns a complete plan into pulls, swaps, substitutes, proxies, or purchases.

The server is useful for unconstrained brewing, inventory-first construction, Bracket 3 planning, and fixed-budget precon upgrades. It evaluates bounded complete candidates and says best found under these constraints rather than claiming a universal power score or mathematically perfect deck.

Features

Related MCP server: MTG-MCP

Privacy promise

Your collections, binder names, locations, and physical-deck allocations remain local by default. Local imports are restricted to configured roots. The server does not push decks, modify collections, reserve cards, add marketplace items to a cart, or complete purchases. Optional marketplace pricing sends only the minimum printing requirements and reads credentials from the environment or MCP host secret store.

Installation

Commander Workshop requires Python 3.11 or newer. From a repository checkout:

python -m venv .venv
. .venv/bin/activate
python -m pip install -e .

V1 currently supports POSIX filesystems only. Its immutable publication paths require directory file descriptors, O_DIRECTORY, O_NOFOLLOW, hard links, fsync, and advisory locks; Windows is not supported. The stdio server also expects the verified local inputs prepared next.

Catalog and rules setup

V1 deliberately makes no network request when the server starts. Download the Scryfall Default Cards JSONL gzip through Scryfall's documented bulk-data API, prepare the five-file rules bundle specified in docs/rules-bundle.md, then run the tested offline bootstrap command:

.venv/bin/commander-workshop-bootstrap \
  --data-dir /absolute/path/to/commander-workshop-data \
  --catalog-jsonl-gz /absolute/path/to/default-cards.jsonl.gz \
  --catalog-url https://data.scryfall.io/default-cards.jsonl.gz \
  --catalog-retrieved-at 2026-08-15T12:00:00+00:00 \
  --rules-bundle /absolute/path/to/rules-bundle

Use the actual download URL and retrieval time. --data-dir is a safe install root; it may already contain unrelated files, which the bootstrap never removes or overwrites. The command verifies the gzip and rules, builds a content-addressed environment beneath environments/<sha256>, and publishes an atomic READY marker only after the complete representation is durable. A retry recovers an exact incomplete environment and returns the same version. Published catalog and rules files are exclusive byte copies with no retained stage aliases. Symlinked inputs, hard-link aliases, unexpected sidecars, and conflicting existing content fail closed.

Before building, bootstrap discovers a fully verified READY environment by its versioned input identity, so normal same-input retries create no new stage. Failed stages are inert and may remain for manual inspection; bootstrap never recursively deletes stage content it can no longer prove it owns.

The printed data directory remains the mutable install root, where MCP records are written under records/. The printed catalog and rules paths point into the attested ready version. Use all three values together; directories without a valid READY marker are incomplete bootstrap state and are never returned.

After bootstrap, set COMMANDER_WORKSHOP_IMPORT_ROOTS to one or more existing absolute directories and use the printed values for the other variables. A missing, stale, or invalid critical source fails closed. See the architecture guide for the data flow.

Claude, Codex, and generic stdio configuration

For Claude Desktop or another host using the common JSON shape, copy examples/mcp-config.json and replace its absolute placeholder paths.

Codex can use the same executable from config.toml:

[mcp_servers.commander_workshop]
command = "/absolute/path/to/commander-workshop-mcp/.venv/bin/commander-workshop-mcp"
args = []

[mcp_servers.commander_workshop.env]
COMMANDER_WORKSHOP_DATA_DIR = "/absolute/install-root"
COMMANDER_WORKSHOP_CATALOG_CURRENT = "/absolute/install-root/environments/<printed-sha256>/catalog/current.json"
COMMANDER_WORKSHOP_RULESET = "/absolute/install-root/environments/<printed-sha256>/rules/current.json"
COMMANDER_WORKSHOP_IMPORT_ROOTS = "/absolute/path/to/imports"

Any MCP v2 client can launch that absolute virtual-environment executable as a local stdio subprocess with those environment variables. There is no HTTP service or account setup in v1. A pipx installation is also workable: use the absolute path returned by pipx environment --value PIPX_BIN_DIR joined with commander-workshop-mcp.

End-to-end example: unconstrained brewing

1. Use search_cards to inspect the pinned catalog and load_deck for each complete candidate deck produced during the brew.

2. Call plan_deck with operation build, card pool all_legal, the desired bracket/theme/proxy dimensions, and one to eight complete candidate submissions. Read the returned commander://plans/... resource.

3. Optionally load a collection, call resolve_availability for the winning plan, then call create_fulfillment_plan. Availability remains hypothetical; fulfillment allocates a copy only inside that immutable result.

This flow is unconstrained by inventory while brewing, yet can still show what is on hand and what is missing before the user decides to act. The complete plan_deck request template is schema-validated by the acceptance suite.

End-to-end example: owned-only construction

1. Export the physical collection as ManaBox CSV or a CSV with explicit column mappings, then call load_collection_snapshot in strict mode.

2. Use search_library to locate candidate cards by name, printing, binder, or assembled-deck allocation.

3. Call plan_deck with card pool owned_only and the collection snapshot ID. A candidate with an unowned non-basic card fails the hard constraint.

4. Read the plan and availability resources to see binder pulls and conflicts. A copy already allocated to a deck is reported, not silently treated as free.

Use the complete owned-only request template after replacing its deck and collection IDs with prior tool results.

End-to-end example: Bracket 3 USD/EUR 50 precon upgrade

1. Export or paste the precon and call load_deck; it remains deck intent, not an ownership claim.

2. Load complete upgraded candidates and call plan_deck with operation upgrade, the precon as starting_deck_id, Bracket 3, and either the precon-upgrade-50-usd or precon-upgrade-50-eur scenario preset semantics.

3. Inspect exact additions/cuts, dated bracket evidence, Game Changers, theme facts, and the guaranteed native-currency acquisition bound. Missing required price evidence cannot pass the cap as zero.

4. Optionally resolve inventory, choose pulls/swaps/substitutes/proxies with create_fulfillment_plan, then call price_purchases for the remaining purchase lines. Pricing is informational and never places an order.

The USD 50 request template contains the full scenario, candidate evidence, score definitions, bracket policy, and starting-deck field. Change both currency and total policy for the EUR preset.

Supported imports

• ManaBox collection CSV, separating physical binders and registered decks from wishlists or other non-owning lists.

• Generic collection CSV with an explicit mapping for quantity and exact card identity, plus optional printing and location fields.

• Arena-style and common quantity/name/set/collector-number deck text.

• User-exported deck text from Moxfield, Archidekt, Deckbox, Deckstats, TopDecked, and similar hosts when it matches the supported text dialect.

Paste or select an export you are authorized to use. V1 does not scrape account pages, reuse browser cookies, or call undocumented deck-host endpoints. Direct hosted URLs return unsupported_source; export the deck and import its text.

Tools

The public surface is exactly eleven tools:

Every tool returns a versioned envelope with a stable result ID, status, concise summary, issues, source stamps, and usually a resource URI.

Resources

commander://cards/{oracle_id}
commander://searches/{result_id}
commander://collections/{snapshot_id}
commander://decks/{deck_id}
commander://plans/{plan_id}
commander://availability/{resolution_id}
commander://prices/{snapshot_id}
commander://fulfillment/{plan_id}
commander://rules/current
commander://presets

Records are immutable and content-addressed. Collections and broad searches are bounded and paginated; tool summaries avoid echoing collection contents.

Scenario dimensions

A planning scenario composes these independent choices:

• operation: build, upgrade, or analyze;

• bracket: 1 through 5, with dated turn and Game Changer evidence;

• card pool: all_legal, prefer_owned, or owned_only;

• budget: native currency total and optional per-card cap, including USD/EUR 50 precon-upgrade presets;

• proxy policy: none, owned-once, or unlimited where the playgroup permits it;

• theme policy: strict contract, flexible preference, or strength-oriented;

• protected assembled decks, pinned ruleset, and deterministic seed.

Bracket fit and strategic power are not collapsed into one score. Official Commander rules remain authoritative, and Rule Zero overrides must be explicit.

Pricing semantics

price_purchases separates item subtotal, provider subtotal, shipping, and estimated landed total. Unknown items or shipping remain null, never zero. A guaranteed budget can pass only when every required purchase has eligible known evidence under the selected policy.

Scryfall catalog values are indicative PriceEstimate observations, not checkout quotes. CardTrader listings are read-only PurchaseQuote observations. Planning estimates use a declared freshness window of at most 24 hours; CardTrader may use a shorter listing lifetime. Partial and stale observations carry explicit unknown_price, authentication, outage, or rate-limit issues.

Provider limitations

• Scryfall estimates come from the verified local catalog, may lack a currency, finish, condition, language, quantity, or shipping, and are not purchasable.

• CardTrader is optional, requires CARDTRADER_API_TOKEN, uses only fixed documented GET endpoints, does not follow redirects, and does not optimize a perfect multi-seller basket.

• Cardmarket and TCGplayer are not enabled by default; access restrictions and provider terms must be respected by any future adapter.

• No provider can change deck legality, collection ownership, proxy policy, or reserve inventory. No provider exposes cart or purchase operations.

Normal tests and CI make no live marketplace or deck-host requests.

Development

python -m pip install -e '.[test]'
python scripts/check_public_tree.py
ruff check src tests scripts
pytest -q
python -m build

The privacy scanner inspects the tracked tree for private paths, credentials, databases, unsafe data exports, symlinks, and undocumented/oversized fixtures. All test data is synthetic and deterministic.

Architecture

See docs/architecture.md for component boundaries, immutable storage, trust boundaries, planning/fulfillment flow, and extension points.

Security reporting

Follow SECURITY.md. Use a private security advisory and a minimal synthetic reproduction; never attach a collection export, binder inventory, token, or other personal data.

Attribution

Card names, rules text, and catalog metadata may be derived from Scryfall, whose data and attribution requirements apply. Magic: The Gathering rules and Commander bracket policy are published by Wizards of the Coast. Provider names and marketplace data remain the property of their respective owners.

Non-affiliation

Commander Workshop MCP is unofficial fan software. It is not affiliated with, endorsed, sponsored, or approved by Wizards of the Coast, Scryfall, CardTrader, or any other deck host or marketplace. Magic: The Gathering, Commander, and related marks belong to Wizards of the Coast and their respective owners.

Commander Workshop MCP is unofficial Fan Content permitted under the Fan Content Policy. Not approved/endorsed by Wizards. Portions of the materials used are property of Wizards of the Coast. ©Wizards of the Coast LLC.

License

The software is released under the MIT License. Third-party card, rules, and marketplace data remains subject to its own terms and licenses.