Document Endpoints

Document endpoints let you retrieve individual legal documents and list collections with filtering and sorting. Each source has its own pair of endpoints following the same pattern.

U.S. Code

List USC Documents

GET /api/usc/documents

Returns a paginated list of USC sections with optional filtering and sorting.

Query parameters:

Example — list sections in Title 17:

curl "https://lexbuild.dev/api/usc/documents?title_number=17&limit=5"

{
  "data": [
    {
      "id": "usc-t17-s101",
      "identifier": "/us/usc/t17/s101",
      "source": "usc",
      "metadata": {
        "display_title": "17 U.S.C. SS 101 - Definitions",
        "title_number": 17,
        "title_name": "Copyrights",
        "section_number": "101",
        "section_name": "Definitions",
        "chapter_number": "1",
        "chapter_name": "Subject Matter and Scope of Copyright",
        "legal_status": "law",
        "positive_law": true,
        "status": "in_force"
      }
    }
  ],
  "meta": {
    "api_version": "v1",
    "format_version": "1.0",
    "timestamp": "2026-04-04T12:00:00.000Z"
  },
  "pagination": {
    "total": 463,
    "limit": 5,
    "offset": 0,
    "has_more": true,
    "next": "/api/usc/documents?title_number=17&sort=identifier&offset=5&limit=5"
  }
}

Get a Single USC Document

GET /api/usc/documents/{identifier}

Retrieves a single USC section by its identifier. You can use either the shorthand form or the full canonical identifier.

Identifier formats:

Example:

curl https://lexbuild.dev/api/usc/documents/t17/s106

{
  "data": {
    "id": "usc-t17-s106",
    "identifier": "/us/usc/t17/s106",
    "source": "usc",
    "metadata": {
      "identifier": "/us/usc/t17/s106",
      "source": "usc",
      "display_title": "17 U.S.C. SS 106 - Exclusive rights in copyrighted works",
      "title_number": 17,
      "section_number": "106",
      "section_name": "Exclusive rights in copyrighted works",
      "chapter_number": "1",
      "chapter_name": "Subject Matter and Scope of Copyright",
      "legal_status": "law",
      "positive_law": true,
      "status": "in_force",
      "source_credit": "Office of the Law Revision Counsel"
    },
    "body": "Subject to sections 107 through 122, the owner of copyright..."
  },
  "meta": {
    "api_version": "v1",
    "format_version": "1.0",
    "timestamp": "2026-04-04T12:00:00.000Z"
  }
}

Code of Federal Regulations

List CFR Documents

GET /api/cfr/documents

Returns a paginated list of CFR sections with optional filtering and sorting.

Query parameters:

Example — list CFR sections from the SEC (Title 17):

curl "https://lexbuild.dev/api/cfr/documents?title_number=17&limit=3"

Get a Single CFR Document

GET /api/cfr/documents/{identifier}

Retrieves a single CFR section. Identifiers follow the same shorthand and full-form patterns.

Example:

curl https://lexbuild.dev/api/cfr/documents/t17/s240.10b-5

CFR metadata includes additional regulatory fields:

{
  "data": {
    "id": "cfr-t17-s240-10b-5",
    "identifier": "/us/cfr/t17/s240.10b-5",
    "source": "cfr",
    "metadata": {
      "identifier": "/us/cfr/t17/s240.10b-5",
      "source": "cfr",
      "display_title": "17 CFR SS 240.10b-5 - Employment of manipulative and deceptive devices",
      "title_number": 17,
      "part_number": "240",
      "agency": "Securities and Exchange Commission",
      "authority": "15 U.S.C. 78a et seq.",
      "status": "in_force"
    },
    "body": "It shall be unlawful for any person..."
  },
  "meta": {
    "api_version": "v1",
    "format_version": "1.0",
    "timestamp": "2026-04-04T12:00:00.000Z"
  }
}

Federal Register

List FR Documents

GET /api/fr/documents

Returns a paginated list of Federal Register documents. FR documents default to reverse chronological order.

Query parameters:

Example — list recent EPA rules:

curl "https://lexbuild.dev/api/fr/documents?agency=Environmental+Protection+Agency&document_type=rule&limit=5"

Get a Single FR Document

GET /api/fr/documents/{identifier}

FR documents are identified by their document number.

Example:

curl https://lexbuild.dev/api/fr/documents/2026-06029

FR metadata includes publication-specific fields:

{
  "data": {
    "id": "fr-2026-06029",
    "identifier": "/us/fr/2026-06029",
    "source": "fr",
    "metadata": {
      "identifier": "/us/fr/2026-06029",
      "source": "fr",
      "document_number": "2026-06029",
      "document_type": "rule",
      "publication_date": "2026-03-20",
      "agency": "Environmental Protection Agency",
      "agencies": ["Environmental Protection Agency"],
      "fr_citation": "91 FR 12345",
      "effective_date": "2026-05-19",
      "comments_close_date": null,
      "docket_ids": ["EPA-HQ-OAR-2024-0001"],
      "cfr_references": [{"title": 40, "parts": ["60"]}]
    },
    "body": "AGENCY: Environmental Protection Agency..."
  },
  "meta": {
    "api_version": "v1",
    "format_version": "1.0",
    "timestamp": "2026-04-04T12:00:00.000Z"
  }
}

Content Negotiation

Single-document endpoints support content negotiation. You can request JSON, raw Markdown, or stripped plaintext:

# JSON (default)
curl https://lexbuild.dev/api/usc/documents/t1/s1

# Raw Markdown with YAML frontmatter
curl -H "Accept: text/markdown" https://lexbuild.dev/api/usc/documents/t1/s1

# Plaintext (Markdown formatting stripped)
curl "https://lexbuild.dev/api/usc/documents/t1/s1?format=text"

See Content Negotiation for full details.

Field Selection

Use the fields query parameter to control which parts of the response are returned:

# Get only metadata, skip the body
curl "https://lexbuild.dev/api/usc/documents/t1/s1?fields=metadata"

# Get specific fields
curl "https://lexbuild.dev/api/usc/documents/t1/s1?fields=section_name,status,legal_status"

ETag Caching

Every single-document response includes an ETag header derived from the content hash. Send If-None-Match to avoid re-downloading unchanged content:

# First request
curl -i https://lexbuild.dev/api/usc/documents/t1/s1
# Response includes: ETag: "a1b2c3d4e5f6g7h8"

# Subsequent request with ETag
curl -H 'If-None-Match: "a1b2c3d4e5f6g7h8"' \
  https://lexbuild.dev/api/usc/documents/t1/s1
# Returns 304 Not Modified if content unchanged

Error Responses

If a document is not found, the API returns a 404 with a structured error:

{
  "error": {
    "status": 404,
    "code": "DOCUMENT_NOT_FOUND",
    "message": "No document found with identifier /us/usc/t1/s999"
  }
}

See Error Handling for all error types.