io.github.cyanheads/federal-regulations-mcp-server

Explore the codified Code of Federal Regulations via eCFR in two modes. "structure" walks the CFR hierarchy (all 50 titles, or one title's chapters → parts → sections) to discover a cite when the exact citation is unknown. "search" runs a full-text query across the codified CFR and returns matching sections with their hierarchy path and a snippet. Both modes accept title and part to narrow the scope, so a part surfaced by structure mode can be searched directly instead of filtering a whole title's hits by eye. Both feed regulations_get_cfr_section. Every search result reports which corpus answered it — the synced local mirror or the live eCFR index — and what that corpus covers, in `source` and `sourceScope`.

Fetch public comments on a Federal Register document or a Regulations.gov docket — the unique corpus of what citizens and organizations actually submitted. Provide exactly one targeting parameter: docket_id (all comments in a docket, broadest), document_object_id (comments on one document, from regulations_get_docket), fr_document_number (convenience — resolves the FR number to its Regulations.gov document internally), or comment_id (one comment's full detail and attachments). The list endpoint returns no body text or attachment info — call with comment_id to read a comment's body. When a comment's real content is a PDF/DOCX attachment, the body is a stub and attachmentOnly is true; the attachment download URLs are returned. Requires REGULATIONS_GOV_API_KEY (free at https://api.data.gov/signup/).

Read the codified text at a CFR location via eCFR — current or as of a past date. Answers "what does 40 CFR 50.1 say today?" and "...as of 2019-01-01?". Three locations: title + part + section for one section; title + part alone for the whole part (large parts can be very long, and their appendices are named rather than inlined; prefer a specific section when you know it); title + appendix for one appendix, passing the identifier exactly as regulations_browse_cfr emits it. eCFR retains historical versions back to roughly 2017; a date before coverage is rejected with guidance. Current single-section reads are served from a synced local mirror when available; the source is reported.

Pull a rulemaking docket from Regulations.gov by docket ID (e.g. "EPA-HQ-OAR-2025-0194") — the docket's metadata (title, agency, RIN, abstract) and the documents filed in it (NPRM, final rule, supporting materials). The docket is the folder holding a rule's whole paper trail; each returned document's objectId feeds regulations_find_comments. A docket often contains hundreds of supporting materials — filter document_types to "Proposed Rule"/"Rule" to find the rule documents themselves. Requires REGULATIONS_GOV_API_KEY (free at https://api.data.gov/signup/); the Federal Register and eCFR tools work without it.

Fetch one Federal Register document by its FR document number — full metadata (title, type, agencies, abstract, action, effective/comment dates, RINs) plus the cross-source handles that make this a workflow server. The output carries the docket ID (chain into regulations_get_docket or regulations_find_comments) and the affected CFR parts (chain into regulations_get_cfr_section). Set include_full_text only when the rule body itself is needed — final rules can run tens of thousands of words.

List rules currently open for public comment, filterable by agency slug and topic, sorted by closing date (soonest first). "What can I still weigh in on?" Runs on the Federal Register's open-comment window and is fully functional without a key. When REGULATIONS_GOV_API_KEY is configured, each row is enriched with the comment count from the Federal Register document's embedded Regulations.gov info (no extra rate-limited call). Open one row with regulations_get_document for the full proposal, or pull the comments with regulations_find_comments.

Search the Federal Register — the daily journal of US proposed rules, final rules, notices, and presidential documents (1994–present) — filtering by full-text query, document type, agency slug, publication date range, and whether the rule is open for comment. The primary discovery entry point: results carry the document number (open with regulations_get_document), docket IDs, RINs, and affected CFR parts that chain into the comment and codified-text tools. The Federal Register caps navigation at 50 pages and the match count at 10,000; when a result set is larger, narrow with published_after/published_before rather than paging deeper.