loopclub-mcp

Jam with Claude. An MCP server that turns a described beat into a loopclub link — ready to audition and rent on-chain. It is a pure encoder over loopgen: it holds no keys, talks to no chain, and signs nothing. Your Claude does the musical thinking and calls build_loop; the server bit-packs it and returns a ?jam= deep link. You open the link, audition the loop free, and rent the cells yourself in the app.

 you (to your Claude):  "dark techno — four-on-the-floor kick, off-beat hats, a low C2 synth drone"
        │
        ▼  Claude calls build_loop({ tracks: [...] })
 loopclub-mcp  →  loopgen.encode → toLink → ?jam= link + ASCII grid
        │
        ▼  Claude replies with the link
 you click  →  loopclub opens with the loop pre-loaded  →  "Rent these cells"  →  one signature

Install

Claude Code:

claude mcp add loopclub -- npx -y loopclub-mcp

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "loopclub": { "command": "npx", "args": ["-y", "loopclub-mcp"] }
  }
}

Set LOOPCLUB_ORIGIN to point links at a specific deployment (defaults to https://app.loopclub.xyz — the app subdomain that handles ?jam= links; the apex loopclub.xyz is the landing page and ignores the param):

{ "mcpServers": { "loopclub": {
  "command": "npx", "args": ["-y", "loopclub-mcp"],
  "env": { "LOOPCLUB_ORIGIN": "https://app.loopclub.xyz" }
}}}

Remote (hosted) — add it on claude.ai with no install

The same server runs over MCP's Streamable HTTP transport so claude.ai (Pro/Max) users can add it as a custom connector by URL — no local tooling:

Settings → Connectors → Add custom connector → https://<host>/mcp

The deployed host is mcp.<your-tunnel-domain> (the branded mcp.loopclub.xyz needs loopclub.xyz's DNS moved to Cloudflare — see deploy/). Exact deploy steps for the VPS are in deploy/ (systemd user unit + Cloudflare tunnel rule).

Run it yourself:

npm run build
npm run start:http          # listens on 127.0.0.1:8787 (POST /mcp), front with a proxy

It binds to localhost only and is meant to sit behind a TLS-terminating reverse proxy / Cloudflare tunnel (see deploy/). It is no-auth by design — the server holds no keys, signs nothing, and is a pure stateless encoder, so there is nothing to steal. The risks of a public endpoint are abuse / DoS, not data loss; those are bounded both in-process (body cap, input bounds, host/origin allowlist, rate limit, stateless JSON mode) and at the edge (Cloudflare WAF). Full threat model: SECURITY.md.

Config (env, all optional):

var	default	purpose
PORT	8787	listen port
MCP_BIND_HOST	127.0.0.1	bind address — keep on localhost behind a proxy
MCP_ALLOWED_HOSTS	mcp.loopclub.xyz,localhost,127.0.0.1	Host-header allowlist (DNS-rebind defense)
MCP_ALLOWED_ORIGINS	https://app.loopclub.xyz,https://loopclub.xyz	Origin allowlist (absent Origin = allowed; foreign = 403)
MCP_MAX_BODY_BYTES	65536	request body cap
MCP_RATE_MAX / MCP_RATE_WINDOW_MS	120 / 60000	coarse per-IP rate limit (Cloudflare is primary)
LOOPCLUB_ORIGIN	https://app.loopclub.xyz	origin baked into emitted ?jam= links

What it exposes

Tools

• build_loop({ tracks, name? }) → { deepLink, asciiGrid, cellCount, instruments, note }. The core. tracks mirror a loopgen LoopSpec: drum tracks carry lit steps (0–15); the synth track carries notes ({ step, pitch }, pitch as MIDI or a name like "C3").
• describe_loop({ link } | { pattern, synthData? }) → a per-track summary + the ASCII grid. Reads a ?jam= link a user pasted, or raw wire bigints.

Resources (so Claude generates good loops, not random cells)

• loopclub://vocabulary — the grid rules, pitch range, and how to be musical.
• loopclub://genres — worked example loops (house, techno, boom-bap, dnb) as ASCII + spec, for few-shot grounding.
• loopclub://how-it-works — the free-audition / paid-press lifecycle.

Prompt

• jam({ genre?, bpm? }) — a one-click entry point that tells Claude to read the resources, build something idiomatic and in-key, and return the link.

Design boundary (deliberate)

• No signing, no keys, no wallet, no chain reads. The server only produces links; the user signs rent in the app. This is why session keys / PR #6 are irrelevant here.
• Stateless. Same spec in → same link out. Restartable, trivially scalable if hosted later (a remote Streamable-HTTP build is a fast-follow).
• The musical engine is entirely loopgen; this package is ~3 small files of glue (schemas → handlers → server).

Develop

npm install          # pulls loopclub-loopgen from npm
npm test             # vitest — handler logic + loopgen round-trip
node scripts/smoke.mjs   # end-to-end: spawns the server, drives real JSON-RPC
npm run build        # tsc → dist/ (bin: loopclub-mcp)

loopgen — the musical codec this server encodes with — is published separately as loopclub-loopgen and developed in the loopclub monorepo. A change to the on-chain wire format means a new loopgen release and a bump here.