Federal Register MCP Server

Federal Register MCP Server is an open-source Model Context Protocol server from BLEN, Inc. that connects MCP clients such as Claude Desktop to three official U.S. government sources: the Federal Register, the eCFR, and regulations.gov. It is released under Apache-2.0 and is read-only. BLEN states it is available in Gemini for government services and works with other MCP clients.

What It Is

The server lets an AI assistant answer questions about federal regulations using official records. Rather than exposing many narrow tools, it gives the model a small documented SDK (fr, ecfr, regs) and lets the model write the exact JavaScript query it needs, a pattern the README calls code mode. Answers cite the identifier and link of each record used.

How the workflow runs

Three tools are exposed: search_api finds the right endpoint using BM25 over the SDK docs, describe_schema looks up an exact call or namespace, and execute runs the JavaScript in a sandbox. For example, a user can ask which proposed rules would change drinking water standards; the agent queries the Federal Register for rules, the eCFR for current section text, and regulations.gov for dockets and public comments.

Sandbox and security model

User code runs in an isolated-vm sandbox, with Deno as a fallback, with no network, filesystem, environment, or subprocess access. The only outbound path is to the three government APIs. An AST preflight and wall-clock timeout apply, and a threat model is published in the repository.

Setup path

Run locally with npx -y @blen/fedreg-mcp-server (Node.js 20.19 or later) and add it to Claude Desktop config. It can also be self-hosted as a Streamable HTTP server with OIDC auth, rate limits, and quotas. The regulations.gov source requires a free API key; without it, only the Federal Register and eCFR sources work.

Current Status

The latest listed release is v2.2.1. The project is described as independent and not affiliated with or endorsed by the U.S. government.