MCP Server

The LexBuild MCP server gives AI assistants direct access to the U.S. Code, Code of Federal Regulations, and Federal Register through the Model Context Protocol. Your AI assistant can search, retrieve, and cite over one million legal documents without leaving the conversation.

Quick Install

Add LexBuild to any MCP-compatible client with a single command:

npx @lexbuild/mcp

Or configure it in your client’s MCP settings:

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

See Installation for client-specific setup guides.

What It Provides

Tools

Five read-only tools for searching and retrieving legal content:

Tool	Description
`search_laws`	Full-text search across USC, CFR, and Federal Register
`get_section`	Fetch a single legal section by canonical 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 a Federal Register 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

Two pre-built prompt templates:

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

Transports

The MCP server supports two transports:

Stdio (local) — Runs on your machine via npx @lexbuild/mcp. Used by Claude Desktop, Claude Code, Cursor, and other local MCP clients. This is the default.
Streamable HTTP (hosted) — Available at mcp.lexbuild.dev. No installation required. Useful for remote or web-based clients.

Both transports connect to the LexBuild Data API to fetch content. No local database is needed.

Hosted Endpoint

A hosted MCP server is available at mcp.lexbuild.dev using the Streamable HTTP transport. No API key is required for basic usage. The hosted endpoint is subject to the same rate limits as anonymous API access.

Next Steps

Installation — Client-specific setup guides and configuration
Tools — Detailed tool reference with parameters and examples
Resources & Prompts — URI scheme and prompt templates
Security — Rate limiting, injection defense, and response budgets