MTG Deckbuilder MCP

analyze_deck

Analyze a pasted MTG decklist to check format legality, mana curve, card roles, price, and Commander template gaps. Flags budget concerns.

Instructions

Analyse a pasted decklist (Moxfield, Arena, Archidekt, MTGO or plain 1 Card Name lines).

Reports legality for the format (size, copies, colour identity, bans), mana curve, colour pips vs land sources, card roles (ramp, draw, removal, wipes, tutors...), gaps against a typical Commander template, Game Changers, and total price. Pass commanders if the list doesn't mark them. budget_per_card flags cards above that USD price.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "decklist": "<decklist>"
    },
    "name": "analyze_deck"
  }
}

Input Schema

Name	Required	Default
`format`	No	commander
`decklist`	Yes
`commanders`	No
`budget_per_card`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 28, 2026

TDQS

B3.4/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are supplied, so the description carries the full burden. It does disclose the analysis outputs, how commanders are inferred, and that budget_per_card 'flags cards above that USD price', which is useful contextual behavior, but it never states that the tool is read-only/non-mutating, requires no auth, or has any cost/latency characteristics for a tool that also computes prices.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The opening sentence front-loads the verb, resource and accepted input formats, with the report scope and the two parameter notes following compactly. It is dense but list-like and every clause contributes; only the parenthetical format list and the role examples add bulk.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so the return shape need not be described (the enumeration is a bonus, not a requirement). However, the tool takes four parameters with zero schema documentation and the description leaves `format` entirely unexplained, leaving an agent unable to know which format strings are valid or how legality is determined.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate — and it partially does: commanders (only needed if the list doesn't mark them) and budget_per_card (USD threshold that flags cards) are explained. The `format` parameter, which drives the entire legality section and defaults to commander, is never described or given its allowed values.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb (analyse) and resource (a pasted decklist) plus the accepted input dialects, and enumerates the report contents (legality, mana curve, pips vs land, roles, template gaps, Game Changers, price), which makes its scope concrete and distinct from sibling card-lookup tools. It never names a sibling explicitly, so it stops short of a 5; the implicit overlap with price_decklist is left unaddressed.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is a conditional instruction for one parameter ('Pass `commanders` if the list doesn't mark them'), which is real usage guidance, but nothing tells the agent when to reach for analyze_deck over price_decklist or the EDHREC/search tools. Usage is only implied by the enumeration of report contents.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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