Full-text search across the CFR for a free-text query or phrase.

Search the CFR using a list of distinct keywords/terms rather than a single free-text phrase.

Keywords are joined into one query string before searching — for precise multi-word phrase search, use search_regulations instead.

Retrieve the exact legal text of one CFR section (e.g. 40 CFR 261.10).

Retrieve the text of an entire CFR part (a cluster of related sections).

Prefer retrieve_section when the clause maps to one exact section — a part's response can be large.

Retrieve the text of an entire CFR title.

WARNING: some titles (notably Title 40 / EPA) are large enough that this can be slow or time out upstream. Strongly prefer retrieve_part or retrieve_section when you know which part or section is relevant — use this only for small titles or genuinely title-wide questions.

Fetch the hierarchical structure of a CFR title (no regulation text) — useful for planning which part/section to retrieve next.

Fetch point-in-time version history for a CFR title, optionally scoped to a part/section and/or filtered by an issue-date range.

Use this to determine which version of a regulation was in effect on a specific date (e.g. when a contract was signed), as opposed to retrieve_section/retrieve_part/retrieve_title, which return the text as of a date but not its full change history.

List all agencies referenced in the CFR, with their title/chapter cross-references.

Useful for mapping a contract clause's implied regulator (e.g. "environmental", "labor", "acquisition") to the correct CFR title before running search_regulations or search_by_keyword.

Returns: On success: {"agencies": [...as returned by eCFR, including nested child agencies...]}. On failure: {"error": true, "error_type": ..., "message": ..., "retryable": ...}.