Lorcana MCP Playtest Platform

A local platform for AI-vs-AI Disney Lorcana matches. AI players connect over the Model Context Protocol (Streamable HTTP) and play exclusively through JSON tool calls; humans watch a live visual spectator board in the browser.

• @lorcana/engine — deterministic TypeScript rules engine + JSON effect DSL (turn structure, inkwell, quest/challenge, all keywords, songs, shift, locations, 20-lore win, deck-out, seeded replay).

• @lorcana/card-data — normalizes the official bulk dump (lorcana-api.com) into 2,487 CardDefinitions and auto-generates DSL scripts for every card (see packages/card-data/dist-data/coverage.json for the translation-tier report).

• @lorcana/mcp-server — MCP server (SDK 1.30.0) at /mcp + spectator REST/SSE API.

• @lorcana/ui — React spectator app (dark ink theme, live SSE updates, card art).

• @lorcana/bots — heuristic MCP client that plays both seats (MCP-compliance proof).

Quickstart

npm install                 # at repo root (requires a filesystem that supports symlinks)
npm run build               # builds all packages (card-data → engine → mcp-server → bots → ui)
npm start                   # serves MCP + API + UI on http://localhost:8787

Run an AI-vs-AI match between two decklists (dreamborn/inktable text format):

npx tsx packages/bots/src/run-match.ts \
  --server http://localhost:8787 \
  --deckA "$(cat data/acceptance/deck-emerald-sapphire.txt)" \
  --deckB "$(cat data/acceptance/deck-amber-emerald.txt)" \
  --games 4 --seed 42 --verbose

Then open the printed spectatorUrl (or just http://localhost:8787) to watch live.

Related MCP server: mtg-mcp-server

Connecting your own AI (MCP)

Point any MCP client at http://localhost:8787/mcp (Streamable HTTP transport). Typical session:

1. lorcana_search_cards / lorcana_get_card — explore the card pool (real text + stats).

2. lorcana_validate_deck → lorcana_import_deck — register a 60-card deck (4 Card Name - Subtitle text format; ≤2 inks, ≤4 copies).

3. lorcana_create_match — returns matchId + one seat token per player.

4. Loop: lorcana_get_state (fog-of-war view for your seat) → lorcana_get_legal_actions (fully enumerated, ready-to-submit) → lorcana_play_action. Match ends at 20 lore / deck-out / lorcana_concede.

All tool errors use { ok:false, error:{ code, message } }. State is persisted after every action (data/matches/*.json) — the server resumes matches across restarts.

Card scripts & the effect DSL

Cards contain no code. Every card has a JSON script (dist-data/scripts.json) of triggers / activated abilities / continuous effects over a small effect vocabulary (DRAW, DEAL_DAMAGE, BANISH, ADD_MODIFIER, CHOICE, FOR_EACH, IF, …) with selector-based targeting. Scripts were auto-generated from printed card text:

• full — every ability sentence translated (1,195 cards)

• partial — keywords + some abilities (428)

• vanilla — stats/keywords only (864; they still play correctly as stat cards)

To regenerate: npm run build-data -w @lorcana/card-data. To hand-improve a card, edit its entry in scripts.json following packages/engine/src/effects/dsl.ts.

Known rules limitations

• ~32% of ability sentences are not yet translated (see coverage.json histogram); affected cards play with keywords/stats only. Sets 10–12 are ~72% sentence-matched; set 13 is not in the bulk dump yet.

• Boost / put-under / cost reduction are modeled in the engine; remaining exotic triggers still map to the closest available trigger, and some unique effects (discard→under, play-from-under, deck-ordering) remain documented no-ops.

• Core format deck construction only (≤2 inks). Illumineer's Quest cards excluded.

• Bulk playtest datapoints: run-match.ts --metrics out.jsonl writes one JSON line per game (winner, turns, lore, eventCounts).

See packages/*/README.md for per-package contracts and deviation logs. SPEC.md is the architecture source of truth.