@lexbuild/mcp

Model Context Protocol server for LexBuild. Gives AI agents direct access to U.S. legal sources: the U.S. Code, Code of Federal Regulations, and Federal Register.

Install

npx @lexbuild/mcp

Or install globally:

npm install -g @lexbuild/mcp

Configuration

Claude Desktop

Add to your Claude Desktop MCP config (~/Library/Application Support/Claude/claude_desktop_config.json):

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

Claude Code

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

With an API key (optional, for higher rate limits)

{
  "mcpServers": {
    "lexbuild": {
      "command": "npx",
      "args": ["-y", "@lexbuild/mcp"],
      "env": {
        "LEXBUILD_API_KEY": "lxb_your_key_here"
      }
    }
  }
}

Tools

Tool	Description
`search_laws`	Full-text search across USC, CFR, and Federal Register
`get_section`	Fetch a single legal section by identifier
`list_titles`	List available titles (USC/CFR) or years (FR)
`get_title`	Get title detail with chapters, or year detail with months
`get_federal_register_document`	Fetch an FR document by document number

Resources

URI-addressable legal sections via the lexbuild:// scheme:

lexbuild://us/usc/t{title}/s{section} — U.S. Code section
lexbuild://us/cfr/t{title}/s{section} — CFR section
lexbuild://us/fr/{document_number} — Federal Register document

Prompts

Prompt	Description
`cite_statute`	Generate a Bluebook citation for a USC or CFR section
`summarize_section`	Plain-language summary with audience targeting

Hosted Endpoint

A hosted MCP server is available at mcp.lexbuild.dev using the Streamable HTTP transport. No API key required for basic usage.

Security

All legal text is wrapped with injection defense markers
Response sizes are capped at 256KB to protect model context
SSRF protection via egress host allowlist
Rate limiting per session (anonymous: 60 req/min)

License

MIT