musicwire_compose_guide - get the free MusicXML authoring guide.
musicwire_validate - pay for detailed MusicXML validation.
musicwire_render - pay to queue a MusicXML render.
musicwire_get_job - inspect a render or poll it to completion.
musicwire_verify_provenance - free check of an artifact SHA-256 against signed render receipts.

Local MCP clients such as Claude Code and Cursor run this package over stdio:

npx -y musicwire-mcp

Hosted MCP clients such as Claude Connectors and Smithery use the public Streamable HTTP endpoint served by the Musicwire API:

https://musicwire.5432wire.com/mcp

That hosted endpoint exposes the same tools and needs no Smithery session config (the listed config schema is an empty object). It does not hold a buyer wallet. musicwire_validate and musicwire_render return HTTP 402 Payment Required with the same x402 quote as POST /v1/validate and POST /v1/render. Retry the identical MCP request with Payment-Signature. Compose guide, job polling, and provenance verify stay free.

Over the hosted endpoint, poll musicwire_get_job with repeated short calls instead of one long wait_for_completion hold: the gateway in front of the hosted endpoint times out requests after roughly 29 seconds, while the render itself continues and stays pollable. Long wait_for_completion waits are fine over stdio.

The only requestable render outputs are MP3 for listening and MIDI for editing. Completed renders also include the source MusicXML, NOTICE.txt, and receipt.json.

Paid calls use x402 Exact USDC on Base. The server reads GET /manifest from the configured API and pays on the network that deployment advertises: Base mainnet (eip155:8453) or Base Sepolia (eip155:84532). It retries a 402 Payment Required response with a signed payment automatically, and never logs or persists the private key.

Install

The package requires Node.js 22.5 or newer. Run the stdio server directly from an MCP client with npx -y musicwire-mcp, or point a Streamable HTTP MCP client at https://musicwire.5432wire.com/mcp.

Configuration

Variable	Required	Description
`MUSICWIRE_API_URL`	No	Musicwire base URL. Defaults to `http://127.0.0.1:8787`.
`MUSICWIRE_X402_PRIVATE_KEY`	For paid x402 calls	Throwaway buyer private key, funded on the network the target deployment advertises. `X402_PRIVATE_KEY` is also accepted for compatibility.
`MUSICWIRE_MCP_PAYMENT_MODE`	No	`x402` (default), or the test-only `stub` mode for a loopback API.

The server starts and serves the free tools without a key. The key is read only when a paid call actually receives 402 Payment Required; if it is missing at that point, the tool call fails with an error telling you to set it. Smithery's hosted listing does not collect these variables: declare no session fields, then pay each musicwire_validate / musicwire_render call with Payment-Signature.

stub mode retries challenges with a non-secret test authorization and is rejected unless MUSICWIRE_API_URL points at localhost, 127.0.0.1, or ::1. It is for Musicwire's explicit local stub profile only. Never use it for a remote API. The hosted /mcp endpoint never enables stub auto-pay and never holds a server-side buyer key.

Fund the buyer wallet on the network the target deployment advertises: real USDC on Base mainnet for the hosted deployment, test USDC on Base Sepolia for a local one. This package never picks the network itself, so it cannot pay on a network the server did not quote, and it refuses any advertised network other than those two. Treat the private key as a secret: inject it through your client environment, do not put it in a repository or client configuration file, and rotate it if exposed.

Claude Code

Add this to the project's .mcp.json, substituting the deployed API URL. Keep the private key in the shell environment that starts Claude Code rather than committing it in this file.

{
  "mcpServers": {
    "musicwire": {
      "command": "npx",
      "args": ["-y", "musicwire-mcp"],
      "env": {
        "MUSICWIRE_API_URL": "https://musicwire.example"
      }
    }
  }
}

Before starting Claude Code, export a buyer key funded on the network that deployment advertises:

export MUSICWIRE_X402_PRIVATE_KEY='0x...'
claude

Cursor

Add the same server entry to Cursor's MCP configuration (.cursor/mcp.json for a project, or the equivalent global MCP configuration):

{
  "mcpServers": {
    "musicwire": {
      "command": "npx",
      "args": ["-y", "musicwire-mcp"],
      "env": {
        "MUSICWIRE_API_URL": "https://musicwire.example"
      }
    }
  }
}

Start Cursor from an environment that exports MUSICWIRE_X402_PRIVATE_KEY; do not store the key in the JSON configuration.

Local, zero-cost development

Run Musicwire with its explicit non-production stub profile, then start the MCP server with stub mode:

ARTIFACT_SIGNING_SECRET='replace-with-a-long-random-secret' docker compose up

MUSICWIRE_API_URL='http://127.0.0.1:8787' \
MUSICWIRE_MCP_PAYMENT_MODE=stub \
npx -y musicwire-mcp

The repository's test/mcp-e2e.test.js uses a real stdio MCP session against this payment behavior and exercises every tool. It creates no wallet, uses no credentials, and sends no funds.

Payment behavior

For musicwire_validate and musicwire_render, the package sends the original request first. If Musicwire returns 402, it reads the advertised payment network from GET /manifest, then the x402 client reads the payment requirements, signs an Exact EVM authorization with the configured buyer wallet on that network, and repeats the identical request with Payment-Signature. Musicwire verifies the authorization before work and captures only after quality control passes. Job polling, the compose guide, and provenance verify are free. The hosted Streamable HTTP endpoint returns that 402 to the calling agent instead of paying.

idempotency_key is available on the two paid tools. Reuse it when retrying a request to ensure Musicwire replays the original outcome instead of creating another payment authorization.