modrinth-mcp

An MCP server that wraps the Modrinth API so an AI agent (Claude Code, Claude Desktop, Cursor, …) can search projects, read project/version metadata, and publish Minecraft mods — create projects and upload built jars as new versions.

Tools

Read-only tools work without a token. Anything that writes needs a Modrinth Personal Access Token.

Related MCP server: mc-pack-builder-mcp

Getting a token

Create a PAT at https://modrinth.com/settings/pats with these scopes:

• Read projects

• Read versions

• Create versions

• Write versions

Set it as the MODRINTH_TOKEN environment variable.

Install

As a Claude Code plugin

/plugin marketplace add justinscott12/modrinth-mcp
/plugin install modrinth-mcp@justinscott12

It runs the published npm package under the hood via npx. Claude Code plugins have no token-entry UI, so the server reads its token from the MODRINTH_TOKEN environment variable in the environment Claude Code runs in. Set it before launching Claude Code, e.g.:

# macOS/Linux (add to your shell profile to persist)
export MODRINTH_TOKEN=your-modrinth-pat

# Windows PowerShell (persist for your user)
setx MODRINTH_TOKEN "your-modrinth-pat"

Then restart Claude Code and run modrinth_whoami to confirm. Read-only tools (search, get project/versions) work without a token.

As an MCP server (any client)

Add to your MCP client config (e.g. Claude Desktop claude_desktop_config.json):

{
  "mcpServers": {
    "modrinth": {
      "command": "npx",
      "args": ["-y", "@justinscott12/modrinth-mcp"],
      "env": {
        "MODRINTH_TOKEN": "your-modrinth-pat"
      }
    }
  }
}

Or in Claude Code directly:

claude mcp add modrinth --env MODRINTH_TOKEN=your-modrinth-pat -- npx -y @justinscott12/modrinth-mcp

Environment variables

Example flow

1. modrinth_whoami — confirm auth works.

2. modrinth_create_project — create the project page (created as a draft).

3. modrinth_create_version — upload your built jar(s) with the target game_versions and loaders.

4. Submit the project for review on the Modrinth site when ready.

Note: create_version and create_project publish public content. Only call them when you actually intend to publish.

Development

npm install
MODRINTH_STAGING=1 MODRINTH_TOKEN=your-staging-pat npm start

The server speaks MCP over stdio. stdout is reserved for the protocol; logs go to stderr.

npm test runs the server over stdio against a local stub (no Modrinth calls).

The server ignores SIGINT/SIGBREAK and exits when the client closes stdin. A console Ctrl+C or Ctrl+Break reaches every process on the console, and on Windows npx runs the server through a .cmd shim: if node exited, cmd.exe would keep the pipe open at a Terminate batch job (Y/N)? prompt and every later tool call would hang. Node can't simulate that on Windows, so check it by hand there: send GenerateConsoleCtrlEvent to a shim-launched server and confirm tools/list still answers.

License

MIT