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

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, and publication date range. The primary discovery entry point: results carry the document number (open with regulations_get_document), each issuing agency with its filterable slug, docket IDs, RINs, and affected CFR parts that chain into the comment and codified-text tools. A query ranks by relevance unless order says otherwise; filter-only browsing lists newest first. 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.

Explore the codified Code of Federal Regulations via eCFR in two modes. "structure" lists all 50 titles; with a title, that title\'s top-level divisions (its chapters, or subtitles); and with a title and part, every section and appendix in the part, flattened and paged, each naming the subpart and subject group it sits under — the way to enumerate a part\'s sections without reading its text. "search" runs a full-text query across the codified CFR and returns matching sections with their hierarchy path and a snippet, one result per section, paged. Both modes accept title and part to narrow the scope. 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`.

List Federal Register documents currently open for public comment, sorted by closing date (soonest first) across the whole open window, filterable by document type, agency slug, and topic. "What can I still weigh in on?" Covers proposed rules and the final rules that take comment (direct final and interim final rules) by default; add NOTICE for the much larger set of notices with comment periods. 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 document, or pull the comments with regulations_find_comments.

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: it returns the plain-text body as a window of up to 64,000 characters (max_chars raises it to 200,000), with the body's total length and, when text remains, the offset to resume from. Short documents return whole; major final rules run past a million characters, so page through with offset rather than reading them in one call.

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 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, with an index of its sections and the names of its appendices; title + appendix for one appendix, passing the identifier exactly as regulations_browse_cfr emits it. A section can be written as people cite it — "61", "§ 141.61", or "141.61(c)" in part 141 all read 40 CFR 141.61, and the response names the identifier it read. Text comes back as a window of up to 64,000 characters (max_chars raises it to 200,000) with the total length and, when text remains, the offset to resume from; whole parts run to millions of characters, so page with offset or read a single section. eCFR retains historical versions from 2017 through the title\'s up-to-date date; a date outside that window is rejected with the window named. Current single-section reads are served from a synced local mirror when available; the source is reported.