.codex-plugin— mcp server

<div align="center"> <h1>@cyanheads/musicbrainz-mcp-server</h1> <p><b>Search artists, releases, recordings, works, and labels; traverse relationships; resolve ISRC/ISWC/barcode; fetch cover art via MCP. STDIO or Streamable HTTP.</b> <div>10 Tools • 1 Resource</div> </p> </div>

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Public Hosted Server: https://musicbrainz.caseyjhand.com/mcp

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Tools

Ten read-only tools mapping the three MusicBrainz access modes — search when you have text, lookup (get_* and lookup_identifier) when you hold an MBID or standard identifier, and browse when you need the complete linked set beyond the single page that lookup folds in:

musicbrainz_search_entities

Resolve a name to an MBID with full-text Lucene search.

• Searches one entity type per call: artist, release-group, release, recording, work, or label
• Field-scoped Lucene syntax (e.g. artist:radiohead AND country:GB)
• Surfaces the raw 0–100 relevance score per hit (100 = exact); results stay in MusicBrainz score-descending order, not re-ranked
• Type-specific fields appear only for the relevant entity (ISRCs on recordings, ISWCs on works, artist credit on release-groups/releases/recordings)
• Pagination via limit (1–100) and offset; echoes the effective query and the true upstream total

musicbrainz_get_artist

The 80% artist-detail call.

• Folds discography (release-groups), band-membership / collaboration relationships, aliases, and tags/genres into one request via inc
• External links (Wikidata QID, Discogs, official site) surface as url-rels — chainable to wikidata-mcp-server and friends; this server does not chase them itself
• inc_release_groups and inc_relationships toggle the expensive sub-resources
• Discography and relationships are capped at one page (25); for a prolific artist's complete release-group list, use musicbrainz_browse_entities (target_type=release-group, artist link)

musicbrainz_get_release

One edition's full detail, the level with an actual tracklist.

• Tracklist as media → tracks → recordings, each with length and recording MBID (lengths rendered m:ss, stored as milliseconds upstream)
• Label + catalog number, barcode, country, release date, format, packaging, and text representation (language/script)
• Carries a cover-art availability stub from the WS/2 payload; call musicbrainz_get_cover_art with the release MBID for the actual image URLs

musicbrainz_lookup_identifier

The deterministic path when you already hold a standard identifier — no name search.

• id_type=isrc → recordings (a recording-level code, often shared by several recordings)
• id_type=iswc → works (a composition-level code)
• id_type=barcode → releases (UPC/EAN)
• ISRC and ISWC hit dedicated exact endpoints; barcode is a Lucene search filter, so its results are ranked (exact match scores 100)
• The output kind field tells you which entity type came back

musicbrainz_browse_entities

The complete-enumeration path — a correctness tool, not just convenience.

• Paginates the full linked set: every release-group by an artist, every release on a label, every recording of a work, every release in a release-group
• Pages arbitrarily deep via offset; totalCount is the true upstream total
• Use it whenever a linked set may exceed a page — the get_* tools embed at most one page (25), and a partial list read as complete is a silent correctness gap
• Provide exactly one link MBID matching a valid parent→child relationship for the target_type

musicbrainz_get_cover_art

Cover Art Archive images, kept separate from the release record.

• Front/back flags, image types, full-resolution URLs, and 250/500/1200px thumbnail URLs
• Returns an empty image set (not an error) when the entity has no art — absence of art is information
• Art is served at the release level; a release-group MBID resolves to a representative release's art automatically
• Image URLs are linked, never rehosted — image copyright stays with the rights holders (only the MusicBrainz core metadata is CC0)

Resources

All entity data is also reachable via the get_* tools, so tool-only clients (the majority) lose nothing. There is no resource list() — the corpus is millions of entities; discovery is via musicbrainz_search_entities, not resource enumeration.

Features

Built on @cyanheads/mcp-ts-core:

• Declarative tool and resource definitions — single file per primitive, framework handles registration and validation
• Unified error handling — handlers throw, framework catches, classifies, and formats
• Pluggable auth: none, jwt, oauth
• Swappable storage backends: in-memory, filesystem, Supabase, Cloudflare KV/R2/D1
• Structured logging with optional OpenTelemetry tracing
• STDIO and Streamable HTTP transports

MusicBrainz-specific:

• Type-safe client over the MusicBrainz Web Service v2 (musicbrainz.org/ws/2, JSON) plus the Cover Art Archive
• Process-wide ~1 req/sec token-bucket rate limiter — concurrent requests serialize to stay under MusicBrainz's per-IP ceiling, so multi-tenant load shares one budget
• Response caching keyed on the full request (including the inc set) — MBIDs are stable and entity data changes slowly, keeping most repeat lookups off the wire
• inc-driven lookups fold discography, relationships, tracklists, and external IDs into a single call rather than serial requests
• Retry with backoff over the full fetch + parse pipeline; an HTML error page served under load is classified transient, not as a parse error

Agent-friendly output:

• Provenance on search/browse — the effective query is echoed and the true upstream total is reported, so an agent can tell a partial window from a complete result
• Truncation honesty — get_* tools disclose when an embedded linked list is capped at one page and name musicbrainz_browse_entities as the complete-enumeration path
• Discriminated outputs — musicbrainz_lookup_identifier returns a kind-tagged union (recordings | works | releases) so callers branch on data, not string parsing
• Raw upstream relevance score surfaced as-is (not a fabricated confidence metric), and missing upstream fields are preserved as absent rather than invented

Getting started

musicbrainz-mcp-server is keyless — no API key or account. MusicBrainz does require a descriptive User-Agent with a contact and rate-limits to ~1 request/second per IP; the server ships a default contact so it works out of the box, but operators running a shared or hosted instance should set MUSICBRAINZ_CONTACT to their own email or URL.

Public Hosted Instance

A public instance is available at https://musicbrainz.caseyjhand.com/mcp — no installation required. Point any MCP client at it via Streamable HTTP, with this client config:

{
  "mcpServers": {
    "musicbrainz-mcp-server": {
      "type": "streamable-http",
      "url": "https://musicbrainz.caseyjhand.com/mcp"
    }
  }
}

Add the following to your MCP client configuration file.

{
  "mcpServers": {
    "musicbrainz-mcp-server": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/musicbrainz-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info",
        "MUSICBRAINZ_CONTACT": "[email protected]"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "musicbrainz-mcp-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/musicbrainz-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info",
        "MUSICBRAINZ_CONTACT": "[email protected]"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "musicbrainz-mcp-server": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "MCP_TRANSPORT_TYPE=stdio",
        "-e", "[email protected]",
        "ghcr.io/cyanheads/musicbrainz-mcp-server:latest"
      ]
    }
  }
}

For Streamable HTTP, set the transport and start the server:

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 [email protected] bun run start:http
# Server listens at http://localhost:3010/mcp

Prerequisites

• Bun v1.3.2 or higher (or Node.js v24+).
• No API key. Optionally set MUSICBRAINZ_CONTACT to your email or URL — recommended for any shared or hosted deployment.

Installation

1. Clone the repository:

git clone https://github.com/cyanheads/musicbrainz-mcp-server.git

1. Navigate into the directory:

cd musicbrainz-mcp-server

1. Install dependencies:

bun install

1. Configure environment:

cp .env.example .env
# edit .env and set MUSICBRAINZ_CONTACT (optional but recommended)

Configuration

Configuration is validated at startup via Zod schemas in src/config/server-config.ts.

See .env.example for the full list of optional overrides.

Rate limit and User-Agent

MusicBrainz enforces a ~1 request/second average rate limit per IP across the whole hosted instance and blocks requests without a descriptive `User-Agent` that identifies the application and a contact. This server satisfies both: it sends musicbrainz-mcp-server/<version> (<contact>) as the User-Agent and serializes all upstream calls through a process-wide token-bucket limiter, with response caching to keep repeat lookups off the wire. On a shared or hosted instance every client shares the one limiter, so bulk enumeration via musicbrainz_browse_entities paces accordingly. Set MUSICBRAINZ_CONTACT to your own email or URL when you deploy.

Attribution and licensing

MusicBrainz core entity data is released under CC0 (public-domain dedication) — see the MusicBrainz license. This server stays on that core metadata and does not fetch annotation text (which carries a different, non-CC0 license). Cover art is served by the Cover Art Archive, a joint project of MusicBrainz and the Internet Archive; image URLs are linked, never rehosted, and each image's copyright stays with its rights holders. Cite MusicBrainz and the Cover Art Archive in downstream use.

Running the server

Local development

• Build and run:

  # One-time build
  bun run rebuild

  # Run the built server
  bun run start:stdio
  # or
  bun run start:http

• Run checks and tests:

  bun run devcheck   # Lint, format, typecheck, security, packaging
  bun run test       # Vitest test suite
  bun run lint:mcp   # Validate MCP definitions against the linter rules

Docker

docker build -t musicbrainz-mcp-server .
docker run --rm -e [email protected] -p 3010:3010 musicbrainz-mcp-server

The Dockerfile defaults to HTTP transport, stateless session mode, and logs to /var/log/musicbrainz-mcp-server. OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

Project structure

Development guide

See CLAUDE.md/AGENTS.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — no try/catch in tool logic
• Use ctx.log for request-scoped logging, ctx.state for tenant-scoped storage
• Register new tools and resources via the barrels in src/mcp-server/*/definitions/index.ts
• All upstream calls route through the services — never fetch() MusicBrainz directly, or you bypass the User-Agent, rate limiter, and cache
• Wrap external API data: validate raw → normalize to domain type → return output schema; never fabricate missing fields

Contributing

Issues and pull requests are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

License

Apache-2.0 — see LICENSE for details.