US federal rules taking effect

Measured conclusion: Deep-tested. L2 outcome: tools_ok.

Which published US federal rules take effect between two dates, and which CFR parts they amend?

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Copy this into your MCP client config:

{
  "mcpServers": {
    "US federal rules taking effect": {
      "url": "https://referencesource.org/mcp/rules",
      "transport": "streamable-http"
    }
  }
}

Measured tools (5)

• list_rules_taking_effect read-only

  What lands on me, and when? Lists already-published US federal final rules whose effective date falls between two dates, soonest first, optionally from one agency. Each with the rule title, the agency, the CFR parts amended, the document number, the rule's own DATES paragraph and a verbatim quote of the Federal Register record. This is the compliance-calendar question — use it for "what takes effect in Q4", not for searching the Federal Register by topic.

  Parameters:

  • from (required) — string — ISO start date, inclusive, e.g. "2026-10-01".
  • to (required) — string — ISO end date, inclusive, e.g. "2026-12-31".
  • limit — integer — How many to return, 1–20. Default 20.
  • agency — string — Optional agency filter, matched case-insensitively as a substring of the agency name ("Coast Guard", "aviation"). Call list_agencies for the names as the Federal Register writes them.

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• get_rule read-only

  Everything this register holds for one final rule: title, agency, effective date, the rule's own DATES paragraph, the CFR parts it amends, its publication date, a link to the rule on federalregister.gov, and a verbatim quote of the Federal Register API record it was read from. Document numbers look like "2026-13685" and appear in every other tool's results.

  Parameters:

  • document_number (required) — string — Federal Register document number, e.g. "2026-13685".

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• list_agencies read-only

  Which agencies have rules coming? Returns each agency in this register with how many rules it has taking effect, the soonest and latest of those dates. Call it to get an agency name exactly as the Federal Register writes it before filtering with list_rules_taking_effect — "Federal Aviation Administration", not "FAA".

  Parameters:

  • query — string — Optional case-insensitive substring filter on the agency name.

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• list_rules_amending_cfr_part read-only

  Is anything changing in the part of the CFR I am subject to? Give a CFR title and part — "49 CFR 192", "40 CFR 52", "21 CFR 1308" — and get the already-published final rules that amend it, soonest effective date first, with each rule's DATES paragraph and a verbatim quote. The part is matched whole, so "40 CFR 5" never returns rules about 40 CFR 52.

  Parameters:

  • cfr_part (required) — string — The CFR title and part together, e.g. "49 CFR 192". A bare part number is refused: it is ambiguous across the fifty CFR titles.
  • from — string — Optional ISO date; only rules taking effect on or after it.
  • limit — integer — How many to return, 1–20. Default 20.

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

• verify_quote read-only

  Is this right? Check a claim about a final rule — its effective date, its agency, the CFR parts it amends — against the Federal Register record instead of trusting it. Says whether the claim matches a stored value, appears only in the verbatim quote, or differs (and then what the record says instead). Effective dates are exactly where a confident wrong answer costs money.

  Parameters:

  • claimed_value (required) — string — The value to check, exactly as claimed, e.g. "Terminated" or "2026-10-29".
  • document_number (required) — string — Federal Register document number of the rule the claim is about, e.g. "2026-13685".
  • field — string — Which field the claim is about, if you know it. Without it, every stored field of the record is checked.

  Hints: read-only yes · destructive no · idempotent not declared · open-world no

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Measured by MCPYP probing. Untested fields are omitted, never estimated. Listing is always free; MCPYP never proxies calls or stores user tokens.