mtga-standard-deckupgrader

MTG Arena Standard Deck Upgrader

This skill takes a Standard deck the user already has on Arena and makes it better and more competitive — without rebuilding it. It uses the same method as the Standard deckbuilder (a deck must be legal now, beat the current ladder meta, and be affordable in wildcards), but applies it as a diagnosis-and-swap pass: find the weakest links and the worst matchups, then spend a (usually small) number of wildcards on the changes that help the most.

Two things stay first-class, exactly as in the builder:

• Rarity is shown on every card — in Arena you craft with wildcards of matching rarity, so rarity is the cost. Label each card C / U / R / M.
• Build from what you already own. An upgrade is mostly about spending a handful of wildcards well, so the user's collection matters even more here than in a fresh build.

Work interactively — this is a conversation, not a one-shot transform. The user knows how their deck actually plays and which matchups they keep losing; you know the meta and the card pool. Combine them: ask what's wrong, react to what they tell you, propose swaps in digestible batches, and refine on their feedback. Do not dump a finished 60 and call it done. Talk through your reasoning, surface options, and only write the final files once the user has agreed to the changes. Default to asking rather than assuming.

Start here: paste your decklist

The user provides their current decklist inline in their prompt (pasted text — ideally the Arena export format with a Deck header and optional Sideboard, but a plain <count> <Card Name> list is fine). Parse it: confirm it's 60 maindeck (+ up to 15 sideboard), identify the archetype/centerpiece and colors, label each card's rarity via Scryfall, and verify every card is still legal:standard and on Arena (flag anything rotated out or banned — that's often the first thing to fix).

If the list is malformed or not 60, say what you found and confirm with the user before proceeding.

Ask what's wrong and what they want improved

Before you diagnose anything yourself, ask the user what they think is wrong with the deck and what they want it to do better. They've played it on the ladder; that's information the list can't give you. Ask in plain language (a few questions, not a wall) — for example:

• What does it struggle with? Mana screw/flood, slow or clunky draws, dead cards in hand, running out of gas, no way to close, folding to removal or sweepers.
• Which matchups are you losing? Be specific — "I get run over by mono-red", "control grinds me out", "I lose to the go-wide deck." This is what the meta-teching should target.
• What do you want it to do better, and what's off-limits? Faster/grindier/more resilient; cards you love and want to keep; how many wildcards you're willing to spend.

Let their answers steer the upgrade — their lived experience outranks your own read when they conflict. But if your diagnosis surfaces a problem they didn't mention (a rotated card, a shaky mana base), raise it and ask whether to address it rather than silently changing it.

Load the user's Arena collection

As with the builder, get the user's collection so upgrades favor cards they can play today and only cost wildcards where it matters. The collection lives at .mtg/collection/mtga_collection.txt (a plain <count> <Card Name> export):

• No collection file present → ask the user to export to .mtg/collection/mtga_collection.txt, and recommend the free exporter https://github.com/NthPhantom10/MTGA-collection-exporter. Make clear it's strongly recommended — with it, any upgrade card they already own costs 0 wildcards, which often means the best upgrade is free. If they decline, proceed and cost added cards from zero.
• Collection file present → ask whether it's up to date and whether to use it; offer a re-export with the same tool if stale. Once confirmed, read it fully.

When a collection is in use, treat it as the inventory: prefer owned upgrades, and count wildcard cost only for the cards the user doesn't already own.

Then confirm: budget tier and match type

• Wildcard budget tier (1–5). Caps how many wildcards of each rarity the upgrade may require (the full table is in references/wildcard-budget.md). Because this is an upgrade, the tier is usually much lower than a fresh build — you're spending a few wildcards, not crafting 60 cards. Suggest Tier 1–2 for a light touch-up and make the spend count: prioritize the cheapest swaps that fix the biggest problems first. Count only the copies the user doesn't already own.
• Match type. BO1 ladder (60, no sideboard) or BO3 (60 + 15-card sideboard). For BO3, sideboard upgrades are part of the job; for BO1, all the meta-teching lives in the maindeck.

The deliverable

Always produce two files, saved in their own folder under .mtg/decks/ in the user's current working directory: .mtg/decks/<deck-slug>/deck.md and .mtg/decks/<deck-slug>/arena.txt (create the folder if missing; slug = a short kebab-case deck name, with a suffix like -upgraded if a folder already exists). See "The .mtg workspace" below.

1. An annotated, upgraded decklist (deck.md) — the full improved 60 (+ sideboard for BO3), cards grouped by role (Centerpiece/Payoffs, Creatures, Removal/Interaction, Card Advantage, Other Spells, Lands; plus Sideboard). Every line shows count, card name, rarity (C/U/R/M), and a one-line reason. Include the mana curve, land count, the wildcard-cost breakdown of the changes (commons / uncommons / rares / mythics the user must craft vs the tier cap, owned cards excluded), the match type, and the meta plan. Open with a "Changes" section — each change as — Cut <card> → Add <card> (rarity; reason; "owned" or "craft 1 R"), grouped by the problem it fixes, plus the total wildcards to craft vs the tier.
2. An Arena import list (arena.txt) — exact MTG Arena import format: a Deck header, then <count> <Card Name> per line; a blank line then Sideboard and 15 cards if BO3. Generate it from the upgraded annotated list so they can't drift.

Use the present_files tool to share both — but only at the end, once the user has agreed to the changes through the interactive method below. The files are the record of a conversation, not its opening move.

The .mtg workspace

All of this skill's file I/O lives in a .mtg/ directory in the user's current working directory, conventionally git-ignored (built output and personal collection data, not source).

If there's no clear working directory to write to — e.g. you're running in an interactive chat with no project folder — ask the user where the .mtg/decks/ and .mtg/collection/ directories should live (prompt for a path) before reading or writing anything, and use that location for the rest of the session.

The subdirectories:

• .mtg/decks/ — where upgraded decks are written. Each deck gets its own subfolder, .mtg/decks/<deck-slug>/, holding deck.md and arena.txt. Same decks folder the other skills use.
• .mtg/collection/mtga_collection.txt — the user's Arena collection (owned cards), the inventory that makes owned upgrades free. See "Load the user's Arena collection" above.

(The pasted decklist is taken from the prompt, not a file.)

The method (diagnose, then upgrade)

Full reasoning is in references/methodology.md; the Scryfall recipes are in references/scryfall-syntax.md; the tier/wildcard logic is in references/wildcard-budget.md. Work in this order:

Step 1 — Diagnose the current list, then talk it through with the user

Read the deck for the things that lose games: rotated/illegal cards, an inconsistent or wrong-speed mana base (too few/many lands, taplands in an aggro deck, missing fixing), a clunky curve, weak or redundant cards (win-more, off-plan filler), and thin answers. Note the biggest problems.

Then share a short, readable diagnosis and reconcile it with what the user told you in "Ask what's wrong": where do their complaints and your read agree, and where does your read surface something they didn't raise? Agree on the top 2–3 priorities together before proposing any cards.

Step 2 — Read the meta and find the bad matchups

Pull the current Standard ladder meta (untapped.gg BO1, mtggoldfish) and identify the top decks. Ask which matchups the user is losing. The upgrade should improve the worst real matchups, not just add power in a vacuum.

Step 3 — Rank upgrades by impact per wildcard, owned-first

For each problem, gather candidate fixes from the meta sites and Scryfall (references/scryfall-syntax.md). Scan the collection first — an owned card that fixes the problem is the best upgrade because it costs nothing. Reach for un-owned cards when they're clearly better and worth a wildcard. Favor cheaper-by-rarity cards that do most of the job (a common/uncommon answer over a premium rare when close).

Step 4 — Choose the swaps and fit the tier

For every add, name the cut (the weakest card in the same or a lower-priority role). Keep the deck at exactly 60 (+15 sideboard for BO3), max 4 of any non-basic card. Compute the wildcard cost of the changes, counting only un-owned copies, and keep it within the tier — if it's over, downgrade the most expensive crafts to an owned card or a cheaper role-equivalent first, or trim copies. Match sweepers and answers to the user's own board (don't add a wrath that kills your own go-wide plan).

Step 5 — Propose, discuss, and iterate (don't write files yet)

Present the proposed swaps to the user for reaction before finalizing — ideally in small batches by priority (e.g. "first, the mana base", then "the aggro matchup"), each as Cut → Add, rarity, why, owned/craft cost, with the running wildcard tally. Invite them to veto, ask why, suggest their own cards, or trade power for fewer wildcards, and adjust accordingly. Where there's a real choice, offer 2–3 options rather than dictating one. Keep going until the user is happy with the full set of changes. Only then assemble the final 60 (+sideboard), run the quality checks below, and write the two files.

Data sources

Same as the builder. Scryfall is the source of truth for Standard legality, rarity, Arena availability, and oracle text (legal:standard, game:arena, r:rare/r:mythic; every card has a rarity field). untapped.gg (https://mtga.untapped.gg/constructed/standard) for the BO1 ladder meta; mtggoldfish (https://www.mtggoldfish.com/metagame/standard) for metagame %s and netdecks.

Scryfall reads come from the local card database. scripts/scryfall_search.py queries a local SQLite database (.mtg/database/cards.sqlite, built from Scryfall bulk data — see the mtg-scryfall-database skill) instead of the API, built automatically on first use (one-time ~540 MB download). At the start, if it reports the data is stale (>30 days), tell the user and ask whether to refresh (for Arena this matters little — only rarity, Arena availability, and Standard legality are used). function:/otag: (Tagger) queries route to the live API automatically.

Retrieval (use what's available, in order):

• Code execution with network → python "${CLAUDE_SKILL_DIR}/scripts/scryfall_search.py" "<query>" --limit 30 to search (reads the local DB, auto-builds on first use; Standard-legal + Arena, rarity shown), and python "${CLAUDE_SKILL_DIR}/scripts/scryfall_search.py" --deck <arena>.txt --tier <N> to tally a list's wildcard cost vs the tier. The script counts every non-basic card from zero — when a collection is loaded, subtract owned copies from its totals yourself.
• No code-exec network, but web tools → web_search then web_fetch (web_fetch only takes URLs from a prior search). No DB can be built here — that's the expected fallback.
• Neither → tell the user the environment needs network to api.scryfall.com, untapped.gg, and mtggoldfish.com, and offer to proceed from known knowledge with the caveat that legality, rarity, and the current meta are unverified (Standard rotates and Arena availability varies — flag this clearly).

Quality bar before you hand it over

• Reconcile the files and the changelog. Generate arena.txt from the upgraded annotated list; verify it sums to exactly 60 (main) and 15 (sideboard, if BO3), max 4 of any non-basic (awk '/^Sideboard/{s=1} /^[0-9]/{if(s)sb+=$1; else md+=$1} END{print "main",md,"side",sb}' arena.txt). The Changes section's cuts and adds must net to zero card-count change; every add appears in the final list and every cut is gone.
• Legality & Arena availability: every non-basic card is legal:standard and on Arena; no banned/rotated cards remain.
• Colors — double-check castability: every nonland card (especially anything you add) is castable in the deck's colors. Vet adds with color identity id<=<colors> (NOT c:, which also matches uncastable multicolor cards), and run python "${CLAUDE_SKILL_DIR}/scripts/scryfall_search.py" --deck arena.txt --colors <wubrg> — it must print COLOR CHECK ✓ (catches e.g. a B/U or B/R card slipped into mono-black).
• Wildcard budget: the rares and mythics the user must craft (owned copies excluded) are within the tier's caps, or the user okayed an overage; commons/uncommons reported as soft. Show the breakdown of the changes.
• Real improvement: the swaps fix the Step 1 problems and improve the worst matchups, the mana base matches the deck's speed, and each change has a clear reason. Only then present the files.