Regulations Tree

Status: stable Category: lookup Added: 2026-07-01 Last reviewed: 2026-10-14

Summary

Returns one CFR part as a nested subpart/section tree, in document order. Use it to build a browse or navigation surface over a part — each leaf entry carries the section number, its official heading, and a stable id, so your application can render the part's structure and fetch individual sections selectively via /api/lookup/regulations/get.

The tree carries headings only, never section text. It answers "what is in this part and in what order," not "what does this section say."

Endpoint

Field	Value
Method	`GET`
Path	`/api/lookup/regulations/tree`
Full URL	`https://engine.tripod-health.com/api/lookup/regulations/tree`
Authentication	API key (required)
Request body	none
Response body	`application/json`
Idempotent	Yes
Rate-limited	Yes

Authentication

Send a valid API key in the apikey header. See authentication.md.

Request

Headers

Header	Required	Description
`apikey`	Yes	Consumer API key.

Path parameters

None.

Query parameters

Parameter	Type	Required	Default	Description
`title`	`integer`	Yes	—	CFR title number, `1`–`50`. OSHA recordkeeping lives under title `29`.
`part`	`string`	Yes	—	CFR part number within the title, e.g. `1904`. Treat as opaque text.

Both parameters are required. Omitting or malforming either returns 400 ValidationError naming the offending parameter.

Body

None.

Response

Success — `200 OK`

The response is the whole part as one nested object: the part's heading, then one node per subpart in document order, each holding its leaf entries in document order. Leaf entries are either regulation sections or appendices, distinguished by type.

The example below is the complete response for 29 CFR part 1904 (?title=29&part=1904): seven subparts and 34 leaf entries. Leaf entries are shown one per line for readability; the JSON is unchanged.

{
  "cfr_title": 29,
  "part": "1904",
  "heading": "PART 1904—RECORDING AND REPORTING OCCUPATIONAL INJURIES AND ILLNESSES",
  "children": [
    {
      "type": "subpart",
      "subpart": "A",
      "heading": "Subpart A—Purpose",
      "children": [
        { "type": "regulation", "id": 102434, "section": "1904.0", "heading": "Purpose." }
      ]
    },
    {
      "type": "subpart",
      "subpart": "B",
      "heading": "Subpart B—Scope",
      "children": [
        { "type": "regulation", "id": 102436, "section": "1904.1", "heading": "Partial exemption for employers with 10 or fewer employees." },
        { "type": "regulation", "id": 102437, "section": "1904.2", "heading": "Partial exemption for establishments in certain industries." },
        { "type": "regulation", "id": 102438, "section": "1904.3", "heading": "Keeping records for more than one agency." },
        { "type": "appendix", "id": 102439, "section": "Non-Mandatory Appendix A to Subpart B of Part 1904", "heading": "Non-Mandatory Appendix A to Subpart B of Part 1904—Partially Exempt Industries" }
      ]
    },
    {
      "type": "subpart",
      "subpart": "C",
      "heading": "Subpart C—Recordkeeping Forms and Recording Criteria",
      "children": [
        { "type": "regulation", "id": 102441, "section": "1904.4", "heading": "Recording criteria." },
        { "type": "regulation", "id": 102442, "section": "1904.5", "heading": "Determination of work-relatedness." },
        { "type": "regulation", "id": 102443, "section": "1904.6", "heading": "Determination of new cases." },
        { "type": "regulation", "id": 102444, "section": "1904.7", "heading": "General recording criteria." },
        { "type": "regulation", "id": 102445, "section": "1904.8", "heading": "Recording criteria for needlestick and sharps injuries." },
        { "type": "regulation", "id": 102446, "section": "1904.9", "heading": "Recording criteria for cases involving medical removal under OSHA standards." },
        { "type": "regulation", "id": 102447, "section": "1904.10", "heading": "Recording criteria for cases involving occupational hearing loss." },
        { "type": "regulation", "id": 102448, "section": "1904.11", "heading": "Recording criteria for work-related tuberculosis cases." },
        { "type": "regulation", "id": 102449, "section": "1904.13-1904.28", "heading": "[Reserved]" },
        { "type": "regulation", "id": 102450, "section": "1904.29", "heading": "Forms." }
      ]
    },
    {
      "type": "subpart",
      "subpart": "D",
      "heading": "Subpart D—Other OSHA Injury and Illness Recordkeeping Requirements",
      "children": [
        { "type": "regulation", "id": 102452, "section": "1904.30", "heading": "Multiple business establishments." },
        { "type": "regulation", "id": 102453, "section": "1904.31", "heading": "Covered employees." },
        { "type": "regulation", "id": 102454, "section": "1904.32", "heading": "Annual summary." },
        { "type": "regulation", "id": 102455, "section": "1904.33", "heading": "Retention and updating." },
        { "type": "regulation", "id": 102456, "section": "1904.34", "heading": "Change in business ownership." },
        { "type": "regulation", "id": 102457, "section": "1904.35", "heading": "Employee involvement." },
        { "type": "regulation", "id": 102458, "section": "1904.36", "heading": "Prohibition against discrimination." },
        { "type": "regulation", "id": 102459, "section": "1904.37", "heading": "State recordkeeping regulations." },
        { "type": "regulation", "id": 102460, "section": "1904.38", "heading": "Variances from the recordkeeping rule." }
      ]
    },
    {
      "type": "subpart",
      "subpart": "E",
      "heading": "Subpart E—Reporting Fatality, Injury and Illness Information to the Government",
      "children": [
        { "type": "regulation", "id": 102462, "section": "1904.39", "heading": "Reporting fatalities, hospitalizations, amputations, and losses of an eye as a result of work-related incidents to OSHA." },
        { "type": "regulation", "id": 102463, "section": "1904.40", "heading": "Providing records to government representatives." },
        { "type": "regulation", "id": 102464, "section": "1904.41", "heading": "Electronic submission of Employer Identification Number (EIN) and injury and illness records to OSHA." },
        { "type": "regulation", "id": 102465, "section": "1904.42", "heading": "Requests from the Bureau of Labor Statistics for data." },
        { "type": "appendix", "id": 102466, "section": "Appendix A to Subpart E of Part 1904", "heading": "Appendix A to Subpart E of Part 1904—Designated Industries for § 1904.41(a)(1)(i) Annual Electronic Submission of Information From OSHA Form 300A Summary of Work-Related Injuries and Illnesses by Establishments With 20-249 Employees in Designated Industries" },
        { "type": "appendix", "id": 102467, "section": "Appendix B to Subpart E of Part 1904", "heading": "Appendix B to Subpart E of Part 1904—Designated Industries for § 1904.41(a)(2) Annual Electronic Submission of Information From OSHA Form 300 Log of Work-Related Injuries and Illnesses and OSHA Form 301 Injury and Illness Incident Report by Establishments With 100 or More Employees in Designated Industries" }
      ]
    },
    {
      "type": "subpart",
      "subpart": "F",
      "heading": "Subpart F—Transition From the Former Rule",
      "children": [
        { "type": "regulation", "id": 102469, "section": "1904.43", "heading": "Summary and posting of the 2001 data." },
        { "type": "regulation", "id": 102470, "section": "1904.44", "heading": "Retention and updating of old forms." },
        { "type": "regulation", "id": 102471, "section": "1904.45", "heading": "OMB control numbers under the Paperwork Reduction Act" }
      ]
    },
    {
      "type": "subpart",
      "subpart": "G",
      "heading": "Subpart G—Definitions",
      "children": [
        { "type": "regulation", "id": 102473, "section": "1904.46", "heading": "Definitions." }
      ]
    }
  ],
  "request_id": "13b660c9-18e8-4789-b88a-380ed16e8dd7",
  "timestamp": "2026-10-14T00:16:22.728Z"
}

Response fields

Field	Type	Always present	Description
`cfr_title`	`integer`	Yes	Echoes the requested title.
`part`	`string`	Yes	Echoes the requested part.
`heading`	`string`	Yes	Official part heading as published in the CFR.
`children`	`array`	Yes	Subpart nodes in document order.
`children[].type`	`string`	Yes	Always `subpart` at this level.
`children[].subpart`	`string`	Yes	Subpart letter, e.g. `"C"`.
`children[].heading`	`string`	Yes	Official subpart heading.
`children[].children`	`array`	Yes	Leaf entries within the subpart, in document order.
`children[].children[].type`	`string`	Yes	`regulation` or `appendix`.
`children[].children[].id`	`integer`	Yes	Stable identifier for the entry. Use it to enumerate what to fetch via `/api/lookup/regulations/get`.
`children[].children[].section`	`string`	Yes	Section number (e.g. `"1904.5"`), a reserved range (e.g. `"1904.13-1904.28"`), or the full appendix designation.
`children[].children[].heading`	`string`	Yes	Official heading of the section or appendix. Headings only — the tree never carries section text.
`request_id`	`string`	Yes	Correlation ID. Quote in support tickets.
`timestamp`	`string` (ISO 8601 UTC)	Yes	Server time when the response was emitted.

Status codes

Code	Meaning	When
`200`	OK	Part found; tree returned.
`400`	`ValidationError`	`title` missing or not an integer `1`–`50`, or `part` missing or malformed. `field` names the offender.
`401`	`Unauthenticated`	Missing or invalid API key.
`404`	`NotFound`	No part matches `(title, part)`.
`429`	`RateLimited`	Per-consumer rate limit exceeded.
`500`	`InternalError`	Unexpected failure. Quote `request_id` in the ticket.

Examples

curl

curl -sS "https://engine.tripod-health.com/api/lookup/regulations/tree?title=29&part=1904" \
  -H "apikey: $ENGINE_API_KEY"

Python (`requests`)

# Uses the call() helper from quickstart.md.
tree = call("GET", "/api/lookup/regulations/tree?title=29&part=1904")
for subpart in tree["children"]:
    print(subpart["heading"])
    for entry in subpart["children"]:
        print(f"  {entry['section']}: {entry['heading']}")

Node.js (native `fetch`)

// Uses the call() helper from quickstart.md.
const tree = await call("GET", "/api/lookup/regulations/tree?title=29&part=1904");
const leaves = tree.children.flatMap((s) => s.children);
console.log(`${tree.part}: ${leaves.length} entries`);

Error scenarios

Missing parameter

Send:

curl -sS "https://engine.tripod-health.com/api/lookup/regulations/tree?title=29" \
  -H "apikey: $ENGINE_API_KEY" \
  -w "\nHTTP %{http_code}\n"

Receive (400):

{
  "timestamp": "2026-10-14T00:16:22.995Z",
  "error": "ValidationError",
  "message": "Query parameter 'part' is required",
  "field": "part",
  "request_id": "528811c3-b323-4e55-989c-a89a2e6a43d6"
}

Unknown part

Send:

curl -sS "https://engine.tripod-health.com/api/lookup/regulations/tree?title=29&part=9999" \
  -H "apikey: $ENGINE_API_KEY" \
  -w "\nHTTP %{http_code}\n"

Receive (404):

{
  "timestamp": "2026-10-14T00:16:23.344Z",
  "error": "NotFound",
  "message": "No part '9999' in CFR title 29",
  "request_id": "018f464a-b09b-4772-9edb-81029565c9f7"
}

Intended use

Building a browse/navigation UI over a part — the tree is already in document order and grouped by subpart, so it renders directly as a sidebar or table of contents.
Enumerating a part's sections to fetch selectively. Walk the leaves, pick the sections you need, and pull their full text via /api/lookup/regulations/get — one tree call replaces guessing at section numbers.
Detecting appendices. Appendices do not follow the part.section numbering scheme; the tree is the reliable way to discover they exist and what they are called.

Mistaken use

Do not use the tree for text search. The tree matches nothing — it returns structure. Use /api/lookup/regulations/search to find sections by content.
Do not expect section text. Leaf entries carry headings only. Use /api/lookup/regulations/get to fetch the full text of a section or appendix.
Do not parse section as a number. Values include reserved ranges ("1904.13-1904.28") and full appendix designations. Treat the field as opaque display text and use id for lookups.

Debugging

Capture request_id from the response body (or, if the response has no body from the engine, the X-Request-ID response header).
400 ValidationError — both title and part are required; the field extra names the missing or malformed one. title must be an integer 1–50.
404 NotFound for a part you're sure exists — confirm the title is right. The same part number can exist under one title and not another.
Fewer leaves than you expected — reserved section ranges are collapsed into a single entry (e.g. "1904.13-1904.28"), so the leaf count is lower than the raw section-number span.

Rate limits

See rate-limits.md for the current per-consumer limits.

lookup-regulations-search.md — find sections by text content.
lookup-regulations-get.md — fetch the full text of one section or appendix.
lookup-icd10cm-tree.md, lookup-cpt-tree.md, lookup-fee_schedule-tree.md — the other lookup trees.
authentication.md, errors.md, rate-limits.md, conventions.md — cross-cutting contract rules.

Change history

Date	Change
2026-07-01	Initial publication.
2026-10-14	Moved from `/api/regulations/tree` to `/api/lookup/regulations/tree`. Response shape unchanged. Examples recaptured; the success example now shows the complete part.
2026-10-14	The `X-Request-ID` response header is the gateway's trace ID for the request and does not match `request_id`; quote `request_id` to support.

Summary​

Endpoint​

Authentication​

Request​

Headers​

Path parameters​

Query parameters​

Body​

Response​

Success — 200 OK​

Response fields​

Status codes​

Examples​

curl​

Python (requests)​

Node.js (native fetch)​

Error scenarios​

Missing parameter​

Unknown part​

Intended use​

Mistaken use​

Debugging​

Rate limits​

Related​

Change history​