Install

Requires Node.js 22 or later. The package is published on npm as @shuji-bonji/rfcxml-mcp; npx fetches it on first use, so no global install is needed.

Claude Desktop

Add the following to the MCP configuration file:

{
  "mcpServers": {
    "rfcxml": {
      "command": "npx",
      "args": ["-y", "@shuji-bonji/rfcxml-mcp"]
    }
  }
}

Configuration file locations:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

Claude Code

CLI:

claude mcp add rfcxml -- npx -y @shuji-bonji/rfcxml-mcp

Or write the same mcpServers block as above into:

• Project scope: .mcp.json at the project root
• User scope: ~/.claude.json

Cowork (plugin)

INFO

A Cowork plugin entry is not described in the repository README at v0.6.53. Until it is, register the server with the same command / args as above in the plugin's MCP configuration.

Pin a version

TIP

The 0.6 line publishes patch releases often. Pin the version when a team relies on identical output or when the server runs in CI.

0.6.x ships patch releases frequently. To pin, write the version into the package spec:

{
  "mcpServers": {
    "rfcxml": {
      "command": "npx",
      "args": ["-y", "@shuji-bonji/rfcxml-mcp@0.6.53"]
    }
  }
}

With the CLI: claude mcp add rfcxml -- npx -y @shuji-bonji/rfcxml-mcp@0.6.53.

Global install (optional)

npm install -g @shuji-bonji/rfcxml-mcp

Then:

{
  "mcpServers": {
    "rfcxml": {
      "command": "rfcxml-mcp"
    }
  }
}

Disk cache: RFCXML_CACHE_DIR

By default, fetched RFCs live only in an in-memory LRU cache and are re-fetched after every restart. Set RFCXML_CACHE_DIR to keep them on disk:

{
  "mcpServers": {
    "rfcxml": {
      "command": "npx",
      "args": ["-y", "@shuji-bonji/rfcxml-mcp@0.6.53"],
      "env": { "RFCXML_CACHE_DIR": "/home/you/.cache/rfcxml-mcp" }
    }
  }
}

Layout on disk:

$RFCXML_CACHE_DIR/
├── xml/rfc9293.xml     # RFCXML (RFC 8650 and later)
└── text/rfc6455.txt    # plain text (older RFCs, or XML fetch failures)

Prefetch: rfcxml-prefetch

The package also ships a rfcxml-prefetch CLI that fills the same layout ahead of time, for offline or CI use:

# Fetch a range into $RFCXML_CACHE_DIR (or ~/.cache/rfcxml-mcp when unset)
npx -y -p @shuji-bonji/rfcxml-mcp rfcxml-prefetch --range 9110-9114

# Individual RFCs, explicit directory, re-download even if cached
npx -y -p @shuji-bonji/rfcxml-mcp rfcxml-prefetch --rfc 6455 --rfc 9293 --cache-dir ./rfc-cache --force

Options: --range A-B, --rfc N (repeatable), --cache-dir DIR, --concurrency N (default 3), --force. RFCs already on disk (XML or text) are skipped unless --force is given. RFC numbers must be digits only; --rfc 9110abc exits with code 1.

Pass the same RFCXML_CACHE_DIR to the server

Files saved by rfcxml-prefetch are read only when the MCP server is started with the same RFCXML_CACHE_DIR. Without it the server ignores the prefetched files and fetches again.