MTG Deckbuilder MCP

find_combos

Detect combos already in a deck, find ones one card away with Commander Spellbook, and surface variants needing a different commander or added colors.

Instructions

Find combos already in a deck and combos that are one card away (Commander Spellbook).

Also lists combos that would work with a different commander or by adding colours.

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": "find_combos"
  }
}

Input Schema

Name	Required	Description	Default
`decklist`	Yes
`commanders`	No
`include_steps`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 28, 2026

TDQS

B3.2/5.0

Behavior3/5

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

No annotations are provided, so the description carries the full behavioral burden. It does disclose useful scope behavior (results include off-deck combos requiring a different commander or added colors) and names the data source, Commander Spellbook, but says nothing about rate limits, auth, or result ordering. Given zero annotation coverage, more disclosure is expected.

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?

Two short sentences, front-loaded with the primary function and followed by the supplementary result scope. No padding or repetition; the trailing enumeration earns its place.

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 return values need no explanation, and the description adequately frames what kinds of combos come back. However, for a 3-parameter tool with 0% schema coverage, the missing parameter guidance leaves the definition short of what an agent needs to call it correctly.

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

Parameters2/5

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

Schema coverage is 0% across three parameters, so the description must compensate and does not. It never explains the decklist format, what the commanders parameter is for (nor why it is separate from decklist), or what include_steps changes about the response.

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?

States a specific verb+resource (find combos in a deck) and enumerates three result categories: already-present combos, one-card-away combos, and combos enabled by a different commander or added colors. It does not explicitly differentiate itself from sibling search_combos, which is the obvious adjacent tool.

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?

Usage is implied by the deck-centric framing, but there is no explicit when-to-use statement, no prerequisites, and no named alternative (search_combos, analyze_deck) with the condition that would select it. An agent can infer the intent but must guess at the boundary.

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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