@decibelsystems/tools

Project intelligence for AI coding sessions. A single MCP server that gives Claude (or any MCP client) a durable memory for your project — issues, decisions, friction, roadmap, and more — stored as plain files inside your repo, so the context survives when the chat window doesn't.

29 facade tools (170+ internal handlers) across work tracking, architecture, experiments, design, git forensics, agent coordination, and security. Tested with Claude Desktop, Claude Code, and Cursor. Learn more →

What is this?

When you work with an AI assistant, everything it "knows" about your project lives in the chat — and vanishes when the session ends. The next session starts cold: it re-discovers the same bugs, re-makes the same decisions, forgets why you chose Postgres over SQLite three weeks ago.

Decibel fixes that. It’s an MCP server that lets your AI write project knowledge to disk in a structured way and read it back in any future session. Track an issue in one conversation; a week later, a fresh session asks "what should I work on?" and gets the answer. Record an architecture decision once; it’s there forever. No database to run, no account to create — it’s just YAML and Markdown in a .decibel/ folder in your repo.

Objectives

Decibel is built around a few goals:

• Persistence over recall. Project state should outlive a single chat — so knowledge accrues instead of evaporating.
• Local-first and private. Everything is plain files in your repo. No telemetry, no cloud dependency, no lock-in. You can read, diff, and commit it like any other source.
• One tool, many domains. A handful of "facade" tools (each with an action) cover tracking, decisions, design, security, and coordination — instead of 170 separate tools cluttering the model’s context.
• AI-native, human-readable. Designed for an assistant to drive, but every artifact is something a person can open and understand.
• Works everywhere MCP does. Same tool set across Claude Code, Claude Desktop, Cursor, and custom agents over HTTP.

Contents

• Requirements
• Quick Start
• Connect your AI client — Claude Code · Claude Desktop · Cursor
• Your first 5 minutes
• The tools
• Daemon mode
• Configuration & Pro license
• Data storage
• Environment variables
• Troubleshooting
• Privacy

Requirements

• Node.js ≥ 18 (node --version to check). On macOS, the easiest path is Homebrew: brew install node.
• An MCP-capable client: Claude Code, Claude Desktop, Cursor, or your own.

Quick Start

# Install globally…
npm install -g @decibelsystems/tools

# …or run on demand with npx (no install)
npx @decibelsystems/tools

Then wire it into your AI client below, and initialize your first project.

Connect your AI client

The tool set is identical across every client — only the config file location differs.

Claude Code

Add to .mcp.json in your project root (or ~/.claude.json to make it global — not ~/.claude/settings.json, which holds model/hooks/plugins and is ignored for MCP servers):

{
  "mcpServers": {
    "decibel-tools": {
      "command": "npx",
      "args": ["-y", "@decibelsystems/tools"]
    }
  }
}

Claude Desktop

Edit ~/Library/Application Support/Claude/claude_desktop_config.json (macOS). If the file doesn’t exist yet, create it.

Important — use the login-shell wrapper. Claude Desktop launches with a stripped PATH and often can’t find a bare npx, so the server silently fails to start. Wrapping the command in zsh -lc makes it load your shell profile and find Node, wherever it’s installed:

{
  "mcpServers": {
    "decibel-tools": {
      "command": "/bin/zsh",
      "args": ["-lc", "npx -y @decibelsystems/tools"]
    }
  }
}

After saving, fully quit Claude Desktop (⌘Q, not just the window) and reopen. The server appears under the Desktop group in Settings → Connectors. First launch is slow while npx downloads the package — give it 30–60s.

Prefer a background service? Run the daemon and add it as a custom connector (URL http://127.0.0.1:4888/mcp) instead — no per-app process, shared across clients.

Cursor

Add to ~/.cursor/mcp.json:

{
  "mcpServers": {
    "decibel-tools": {
      "command": "npx",
      "args": ["-y", "@decibelsystems/tools"]
    }
  }
}

Your first 5 minutes

1. Register a project. Tools are scoped to a project, so this comes first. Just ask your assistant:

"Run project_init for this folder."

That creates a .decibel/ directory and registers the project. (Prefer files? Copy projects.example.json to projects.json and add your paths.)

2. Start using it. Everything is plain-language — the assistant maps your request to the right tool:

3. Come back later. In a brand-new session, ask "what’s open and what should I work on?" — and the assistant reads back everything from .decibel/. That’s the whole point.

💡 Tip: Add a short note to your CLAUDE.md (Claude Code) or project instructions (Claude Desktop) telling the assistant to prefer Decibel tools for tracking work — so it reaches for them automatically.

The tools

Every tool is a facade: one tool per domain, with an action parameter selecting the operation (e.g. sentinel + action create_issue).

Core — always available

Pro — requires a license key

Add your license key to ~/.decibel/config.yaml under license.key to unlock Pro. See Configuration.

Daemon mode

Run Decibel as a persistent background service with an HTTP transport — useful when several clients (Desktop, Cursor, custom agents) should share one server and one set of .decibel data.

# Start the daemon (default 127.0.0.1:4888)
npx @decibelsystems/tools --daemon

# Both transports (stdio + HTTP) from one process
npx @decibelsystems/tools --daemon --stdio

# Manage it as a macOS launchd service (auto-start on login)
npx @decibelsystems/tools --daemon install
npx @decibelsystems/tools --daemon uninstall
npx @decibelsystems/tools --daemon status

The daemon includes log rotation, crash-loop protection (5 crashes in 60s), graceful shutdown with request draining, and a /health endpoint. MCP clients connect at http://127.0.0.1:4888/mcp; check it’s alive with curl http://127.0.0.1:4888/health.

Configuration & Pro license

Create ~/.decibel/config.yaml:

daemon:
  port: 4888
  host: 127.0.0.1
  auth_token: your-secret-token   # optional; required for non-localhost
  log_max_size_mb: 10
  log_max_files: 3
  rate_limit_rpm: 60
license:
  key: your-license-key           # unlocks Pro facades

CLI flags override config-file values. Send SIGHUP to reload config without restarting.

Data storage

Everything lives in a project-local .decibel/ folder — readable, diffable, commit-able:

{project}/
└── .decibel/
    ├── sentinel/
    │   ├── issues/      # ISS-{nnnn}.yml
    │   └── epics/       # EPIC-{nnnn}.yml
    ├── architect/
    │   ├── adrs/        # ADR-{nnnn}.yml
    │   └── policies/    # POL-{nnnn}.yaml
    ├── dojo/
    │   ├── proposals/   # DOJO-PROP-{nnnn}.yml
    │   ├── experiments/ # DOJO-EXP-{nnnn}/
    │   └── wishes/      # WISH-{nnnn}.yml
    ├── designer/        # Design decisions, principles, crits
    ├── friction/        # Pain point logs
    ├── learnings/       # Knowledge documents
    ├── context/         # Pinned facts, events
    ├── guardian/        # Security scan results, allowlists
    └── voice/inbox/     # Voice messages (Pro)

Environment variables

Core

Optional integrations

Troubleshooting

Tools don’t show up in Claude Desktop.

1. You almost certainly hit the PATH problem — use the zsh -lc wrapper, not a bare npx.
2. Fully quit (⌘Q) and reopen — a closed window isn’t a restart.
3. First launch downloads the package; wait 30–60s.
4. Check the log: ~/Library/Logs/Claude/mcp-server-decibel-tools.log.

PROJECT_NOT_FOUND errors. Nothing’s registered yet — run project_init (or registry add) for your project before calling other tools.

Local server vs. hosted connector. decibel-tools is a local MCP server — it’s configured in the JSON file and only appears once you add it there. It won’t show up in the connector search (that only lists Anthropic’s hosted catalog). Hosted connectors (GitHub, Gmail) are separate, account-scoped, and enabled per-app and per-conversation.

Pro facades missing. They need a license.key in ~/.decibel/config.yaml (or DECIBEL_PRO=1 in dev).

Privacy

• Local storage only. All project data stays in .decibel/ folders in your repos. Nothing is sent anywhere by default.
• Optional cloud integrations activate only when you configure API keys (Figma, Supabase, OpenAI) — marked openWorldHint: true in their tool annotations.
• No telemetry. No usage analytics, no tracking.

License

MIT — Decibel Systems