theory

theory is an MCP server for Claude Code, Codex, Cursor from DigitalBrewLLC/playbykey-dev-tools. Its token cost is not measured, scanned A, original, MIT.

A local music-theory tool server that lets an AI agent call features from the @playbykey/theory package through MCP, a standard way for agents to use outside tools.

In plain words
What is it for?
Use it for chord, scale, progression, transposition, and related music-theory tasks supported by the package.
Why use it?
It gives the agent a defined interface for music-theory calculations instead of relying only on generated text.

MCP server for Claude CodeCodexCursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add mcp/digitalbrewllc/playbykey-dev-tools/theory
Clone the repo
git clone --depth 1 https://github.com/DigitalBrewLLC/playbykey-dev-tools

Made for: Claude Code, Codex, Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for theory

README.md
[![agentmods](https://agentmods.dev/badge/mcp/digitalbrewllc/playbykey-dev-tools/theory.svg)](https://agentmods.dev/mcp/digitalbrewllc/playbykey-dev-tools/theory)
Your own site
<a href="https://agentmods.dev/mcp/digitalbrewllc/playbykey-dev-tools/theory"><img src="https://agentmods.dev/badge/mcp/digitalbrewllc/playbykey-dev-tools/theory.svg" alt="Measured on agentmods" height="20"></a>
Per session not measured What this adds to a session before it is invoked.
When invoked not measured Not applicable: nothing here is loaded into a session.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Security

Grade A, and why

theory scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.mcp.json · 9 lines

What it actually says

{
  "theory": {
    "command": "npx",
    "args": [
      "-y",
      "@playbykey/theory-mcp"
    ]
  }
}
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 9 lines scan A 6312a0453197

Subscribe to this mod's changes

theory is an MCP server published in the GitHub repository DigitalBrewLLC/playbykey-dev-tools (1 stars, last pushed 1mo ago), licensed MIT. Its token cost is not measured: an MCP server costs its tool schemas, not its config file. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.