Ranks all bundled markdown documents (rules, definitions, control guidance,
agency/assessor/advisor guidance) by BM25 relevance to the query and returns
the best matches with a snippet and the document path. Use the returned
`path` with `fedramp_get_document` to read the full text, or use
`fedramp_get_rule` / `fedramp_get_definition` for a specific ID or term.

Args:
    params (SearchInput):
        - query (str): keywords or a rule ID to search for.
        - section (Optional[str]): path-prefix filter (e.g. 'providers/20x').
        - limit (int): max results, 1-30 (default 8).
        - response_format (ResponseFormat): 'markdown' (default) or 'json'.

Returns:
    str: Ranked results. JSON schema when response_format='json':
    {
      "query": str,
      "count": int,
      "results": [
        {"path": str, "title": str, "section": str,
         "score": float, "snippet": str}
      ]
    }
    Markdown otherwise. Returns a "No matches" message if nothing is found.

Use a `path` returned by `fedramp_search` or `fedramp_list_documents`.

Args:
    params (GetDocumentInput):
        - path (str): repo-relative markdown path, e.g.
          'agencies/rules/agency-use.md'.

Returns:
    str: The document's markdown (frontmatter stripped), prefixed with its
    title and path. Returns an actionable error if the path is unknown.

Useful for browsing the structure before drilling in. Sections include
'advisors', 'agencies', 'assessors', 'authority', 'providers', 'reference',
'responsibilities', plus top-level files (definitions.md, rules.md, ...).

Args:
    params (ListDocumentsInput):
        - section (Optional[str]): path-prefix filter (e.g. 'reference/controls').
        - response_format (ResponseFormat): 'markdown' (default) or 'json'.

Returns:
    str: List of {path, title}. JSON schema when response_format='json':
    {"section": str|null, "count": int,
     "documents": [{"path": str, "title": str}]}

FedRAMP rule IDs look like 'FRC-CSO-FCP', 'VDR-CSO-CVE', 'KSI-IAM-01'; NIST
control IDs look like 'AC-20' or 'SI-4'. The same rule ID often appears in
several documents (e.g. the provider view and the `reference/` rulesets); all
occurrences are returned so you can cite the right context.

Args:
    params (GetRuleInput):
        - rule_id (str): the rule or control ID (case-insensitive).

Returns:
    str: The rule text plus its locations. Markdown by default. Returns an
    actionable error, with close ID suggestions, if the ID is unknown.

Definitions are authoritative: when a defined term appears in a rule, the
definition is part of that rule and must be followed precisely.

Args:
    params (GetDefinitionInput):
        - term (str): a term, alias, or FRD ID (e.g. 'Significant Change',
          'adaptive changes', 'FRD-SGC'). Case-insensitive.

Returns:
    str: The definition, its ID, aliases, and related-terms group. Returns an
    actionable error with suggestions if the term is not defined.