Retrieve the text of a specific CFR citation.

Large parts return an outline of their sections instead of full text; follow up with a specific section citation to read it.

Full-text search across the CFR.

Returns citations, headings and short snippets only — never full text. Follow up with lookup_citation to read anything.

Show which titles/chapters/parts contain a term, with hit counts.

Cheap orientation tool: fetches no regulation text at all. Use this before searching when you don't know which part of the CFR governs a topic.

Return the CFR hierarchy for a title (or one part) without any text.

List amendment dates for a citation, plus any published corrections.

Each amendment is cross-linked to the Federal Register rule that caused it, with a URL to the rulemaking (whose preamble explains the why). Follow up with compare_versions to see exactly what text changed.

Show how a citation's text differs between two dates, as a diff.

Use what_changed first to find amendment dates worth comparing; pass the day before an amendment as date_a and the amendment date as date_b to see exactly what that rule changed. Both dates must be 2017-01-03 or later.

List federal agencies and the CFR titles/chapters they administer.

Use this to turn a name like "EPA" into the right CFR title before searching.