mtg-mcp

mtg-mcp gives an LLM grounded Magic: The Gathering card, deck, provider, and statistical evidence. The LLM makes deckbuilding decisions.

The clean-break 0.9.0 server uses stdio. It exposes 93 tools, one capability resource, and no prompts. It does not migrate 0.8.x data or tool schemas.

Status

The evidence-first rewrite is complete. 0.9.0 is the first stable release of the new surface.

The packaged acceptance run passed 88 tools live. Two Scryfall corpus operations are fixture-backed, Scryfall rollback awaits a second provider generation, and two Playgroup writes remain fixture-only because the public API has no cleanup. See live acceptance.

Start the server

Bootstrap the repository, then run the MCP smoke test:

.\bootstrap.ps1
task smoke:mcp

On Linux or macOS:

./bootstrap.sh
task smoke:mcp

Use mtg-mcp as the MCP command. The default invocation is equivalent to:

mtg-mcp --mode=local --toolsets=default

Use --smoke for a one-shot configuration check. It does not start an MCP session.

Choose a mode

Modes control authority.

local is the default. Scryfall cache misses can require a local write for pacing and evidence persistence. In read-only, those misses return local-write-required before HTTP.

Choose toolsets

Toolsets control relevance. They do not grant authority.

Available toolsets are decks, scryfall, stats, archidekt, and playgroup. Selection is fixed for the MCP session.

Read mtg://server/capabilities to inspect the active mode, toolsets, counts, credential state, package version, and data-store state. Reading the resource does not contact a provider.

Configure the server

Pass configuration on the command line, in environment variables, or in an optional mtg-mcp.json in the working directory. Command-line values win over environment values. Environment values win over JSON.

The default data root is the platform application-data directory under mtg-mcp/v0.9. All MCP processes that use the same root reuse decks.db and scryfall.db. Reads do not create the root.

Configure Archidekt

Use MTGMCP__ARCHIDEKT__USERNAME and MTGMCP__ARCHIDEKT__PASSWORD, or create:

~/.mtg-mcp/archidekt.json

The provider origin is fixed. Authentication output never contains credentials, account identity, or a credential path.

Configure Playgroup

Use MTGMCP__PLAYGROUP__API_KEY, or create:

~/.mtg-mcp/playgroup.json

The file contains one apiKey property. The provider origin is fixed to the official public API.

Work with local decks

The decks toolset supports:

• revisioned deck, entry, zone, category, and provider-binding changes;
• atomic ordered batches;
• guarded backup, restore, and delete;
• native JSON and generic text import and export;
• Archidekt and Moxfield manual artifacts;
• exact Scryfall identity reconciliation; and
• deterministic tag-rule categorization.

Every existing-deck mutation requires expectedRevision. The store is format-neutral. Validation checks structure, not Commander legality, card quality, or strategic fit.

Use deck_identity_reconcile_preview before apply. Resolution uses printing ID, set and collector number, Oracle ID, then exact name. It never uses fuzzy matching or selects an arbitrary printing.

Use deck_category_rules_validate, deck_category_rules_preview, and deck_category_rules_apply to evaluate caller-owned tag rules. Rules can be inline or use the transparent common-v1 preset. The MCP does not decide what a category means.

Import and export decks

Use deck_interchange_formats to inspect preservation limits.

Provider artifacts do not perform network automation. Excluded entries remain in the native companion and are omitted from provider text.

Query Scryfall

The scryfall toolset supports search, exact card lookup, collection lookup, prints, rulings, sets, catalogs, autocomplete, bulk metadata, tag evidence, immutable snapshots, and explicit corpus lifecycle operations.

The local corpus contains All Cards, Rulings, Oracle Tags, and Art Tags. Corpus sync is explicit. It never runs at startup or in the background.

Freshness policies are default, cache-only, and refresh. The default TTL is 24 hours. Immutable snapshots do not expire.

scryfall_card_collection accepts 150 ordered lookup rows. It uses local corpus hits first, deduplicates provider misses, and sends provider batches of at most 75. Results use stable cursor pagination.

Arbitrary Scryfall queries remain provider-authoritative. The cache reuses only the exact same request. Card facts and community tags remain separate evidence classes.

Calculate exact statistics

The stats toolset provides eight read-only tools for:

• univariate and multivariate hypergeometric probability;
• probability-by-turn tables;
• caller-defined mana-source availability;
• package and combo assembly;
• explicit mulligan schedules;
• minimum-copy and minimum-source solving; and
• deterministic deck composition summaries.

Every probability returns an exact reduced fraction and a stable decimal. The caller supplies the population, groups, turn draws, mana capabilities, and keep rules. The MCP does not infer legality, roles, or whether a result is good.

Deck-backed statistics can select entries by entry ID, zone name, or category ID. This lets an LLM use existing Archidekt groups or deterministic categories without hiding the selected cards.

Synchronize Archidekt

Enable the archidekt toolset. Use remote mode for remote writes.

The adapter supports owned deck list/get/create/delete, pull, push, diff, folders, and named snapshots. Apply operations require current revisions, fingerprints, and preview evidence. The MCP never chooses a conflict winner.

Requests start at least two seconds apart per configured account. The adapter allows at most 30 starts in 60 seconds and 150 requests per tool invocation. It stops on 403 and 429. Ambiguous mutations are not retried.

Archidekt may renumber category positions. Content equality therefore compares category identity, membership, flags, and primary assignment, not the provider-controlled numeric rank.

Read Playgroup evidence

Enable the playgroup toolset. It exposes the pinned Public API 1.0.0 surface. All modes include 14 safe read tools. remote adds two write tools.

Results preserve provider JSON and include operation, API version, retrieval time, checksums, and limitations. The adapter does not rank decks or infer quality.

Request starts are at least 250 milliseconds apart. Reads have bounded retry. Writes are single-attempt. Live acceptance does not invoke writes because the public API provides no cleanup operation.

Evidence and safety

The server keeps these output classes distinct:

• provider facts;
• provider evidence;
• exact derivations;
• parser classifications;
• heuristics; and
• sampled estimates.

Stable 0.9.0 contains no advisor prompts, intent inference, weak-card judgments, replacement recommendations, blended quality scores, or strategic simulation. Deferred work is listed in Potential Features.

Develop and verify

Use Task as the command menu:

task --list
task lint
task test
task surface:report
task coverage
task pack
task smoke:process
task smoke:mcp
task release:tool-smoke

Normal tests are deterministic and offline. Live tests require explicit opt-in. Each production assembly must maintain at least 90 percent line coverage.

Architecture

Read North Star, Design Goals, and the rewrite guide for durable constraints.

License

Licensed under the GNU Affero General Public License v3.0 or later.