eCFR

Electronic Code of Federal Regulations REST API for accessing the official US Code of Federal Regulations, searching regulations, and retrieving regulatory version history.

eCFR publishes 3 API contracts indexed on the APIs.io network: Admin Service API, Search Service API, and Versioner Service API. Tagged areas include Federal Regulations, Government, Legal, Compliance, and Open Data.

The eCFR catalog on APIs.io includes 1 Spectral governance ruleset.

eCFR’s developer surface includes documentation, engineering blog, pricing, code examples, and 22 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

23.8/100 emerging ▬ flat Agent 26/100 agent aware Front door AI 1/6 silent saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessFree

1 published contract

Federal RegulationsGovernment Legal Compliance Open Data United States

What this lets a business do 1

Business capabilities this provider's published APIs can perform, derived from its own contracts. Browse all capabilities →

Legislative & Regulatory Drafting Management

BC-3210

Admin ServiceVersioner Service

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 23.8/100 · emerging

Contract Quality 9.3 / 21

Developer Ergonomics 0.0 / 17

Access Clarity 0.9 / 17

Operational Transparency 2.3 / 11

Contract Governance 2.4 / 10

Discoverability 4.9 / 9

Regulatory Posture 2.5 / 15

Agent readiness — 26/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 6 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 9 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 4 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Government & Public Sector regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics does not apply to this provider. The published contracts declare no write operations, and a read-only API cannot create-or-update. The facet is excluded from this provider's denominator entirely — not scored zero. A reference or data API is not deficient for being unable to upsert.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey)
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented)

6 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Developer Ergonomics scores 0.0 — up to +20.0 composite points
Access Clarity scores 5.3 — up to +18.9 composite points
Contract Quality scores 43.7 — up to +14.1 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/ecfr/apis.yml: open an issue on github.com/api-evangelist/ecfr to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Standards implemented 1

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

OpenAPI

1 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Ecfr Rate Limits

1 limits

RATE LIMITS

Service Levels 1

Uptime the provider promises or reports, as SLA4OAI. Read from its own pages; APIs.io runs no monitors.

eCFR

SLA

FinOps 1

Cost, billing, and metering signals for API financial operations.

Ecfr Finops

FINOPS

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

eCFR — jsonschema rules

5 rules · 4 warnings 1 info

SPECTRAL

JSON Schema 7

Standalone JSON Schema definitions for this provider's data models.

AgenciesResponse

1 properties

JSON SCHEMA

Agency

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Ecfr Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Ecfr Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Ecfr Agentic Access

15 operations

15 operations · 0 acting

AGENTIC

Resources

Documentation 8

Reference material describing how the API behaves

Documentation

OpenAPI

JSONSchema

JSONSchema

JSONSchema

JSONSchema

Pricing, plans, and the legal terms of use

Pricing

Pricing

Plans

Plans

FinOps

FinOps

Company 2

The organization behind the API

Website

Website

Blog

Blog

Other 1

Properties that don't map to a standard resource type

CapabilityMap

CapabilityMap

Source (apis.yml)

aid: ecfr
name: eCFR
description: Electronic Code of Federal Regulations REST API for accessing the official US Code of Federal Regulations, searching
  regulations, and retrieving regulatory version history.
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: true
  label: Hosted service · you call their endpoint
  confidence: high
  source:
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: free
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Free
  confidence: low
  source:
  - plans
  - security
  - url: https://www.ecfr.gov
    status: 302
    note: declared website redirects to https://unblock.federalregister.gov/ — a different registrable domain (ecfr.gov ->
      federalregister.gov), possible rename or acquisition (probed 2026-09-03, roadmap#169)
  generated: '2026-11-06'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/ecfr.png
url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/apis.yml
created: '2026-06-13'
modified: '2026-06-13'
specificationVersion: '0.23'
tags:
- Federal Regulations
- Government
- Legal
- Compliance
- Open Data
- United States
apis:
- aid: ecfr:ecfr-admin-service-api
  name: eCFR Admin Service API
  description: Access eCFR metadata through JSON
  humanURL: https://www.ecfr.gov/developers/documentation/api/v1
  baseURL: https://www.ecfr.gov/api/versioner/v1
  tags:
  - Admin Service
  properties:
  - type: OpenAPI
    url: openapi/ecfr-admin-service-api-openapi.yml
  - type: Documentation
    url: https://www.ecfr.gov/developers/documentation/api/v1
- aid: ecfr:ecfr-search-service-api
  name: eCFR Search Service API
  description: Historical search of the eCFR
  humanURL: https://www.ecfr.gov/developers/documentation/api/v1
  baseURL: https://www.ecfr.gov/api/versioner/v1
  tags:
  - Search Service
  properties:
  - type: OpenAPI
    url: openapi/ecfr-search-service-api-openapi.yml
  - type: Documentation
    url: https://www.ecfr.gov/developers/documentation/api/v1
- aid: ecfr:ecfr-versioner-service-api
  name: eCFR Versioner Service API
  description: Access CFR content and structure files through JSON and XML
  humanURL: https://www.ecfr.gov/developers/documentation/api/v1
  baseURL: https://www.ecfr.gov/api/versioner/v1
  tags:
  - Versioner Service
  properties:
  - type: OpenAPI
    url: openapi/ecfr-versioner-service-api-openapi.yml
  - type: Documentation
    url: https://www.ecfr.gov/developers/documentation/api/v1
common:
- type: CapabilityMap
  url: capabilities/ecfr-capability-edges.yml
  name: eCFR Business Capability Map
- type: AgenticAccess
  url: agentic-access/ecfr-agentic-access.yml
- type: VulnerabilityDisclosure
  url: security/ecfr-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/ecfr-domain-security.yml
- type: Website
  url: https://www.ecfr.gov
- type: Documentation
  url: https://www.ecfr.gov/developers/documentation/api/v1
- type: GitHubOrg
  url: https://github.com/usgpo
- type: Blog
  url: https://www.federalregister.gov/blog
- type: Pricing
  url: https://www.ecfr.gov/developers
- type: Plans
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/plans/ecfr-plans-pricing.yml
- type: RateLimits
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/rate-limits/ecfr-rate-limits.yml
- type: FinOps
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/finops/ecfr-finops.yml
- type: OpenAPI
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/openapi/ecfr-openapi.json
- type: JSONSchema
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/json-schema/agency.json
- type: JSONSchema
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/json-schema/cfr-title.json
- type: JSONSchema
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/json-schema/search-result.json
- type: JSONSchema
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/json-schema/content-version.json
- type: JSONSchema
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/json-schema/correction.json
- type: JSONSchema
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/json-schema/cfr-ancestor.json
- type: Vocabulary
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/vocabulary/ecfr-vocabulary.json
- type: JSONLDContext
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/json-ld/ecfr-context.json
- type: Examples
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/examples/titles-response.json
- type: Examples
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/examples/agencies-response.json
- type: Examples
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/examples/search-results-response.json
- type: Examples
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/examples/ancestry-response.json
- type: Examples
  url: https://raw.githubusercontent.com/api-evangelist/ecfr/refs/heads/main/examples/versions-response.json
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

eCFR API — frequently asked questions

Does eCFR have an API?

Yes. APIs.io lists 3 APIs from eCFR, including eCFR Admin Service API, eCFR Search Service API and eCFR Versioner Service API.

Is there an OpenAPI specification for the eCFR API?

Yes. APIs.io indexes 3 OpenAPI specifications for eCFR, each linked for download from this page.

How much does the eCFR API cost?

APIs.io lists 1 pricing plan for eCFR, with each plan's price, limits and inclusions under Pricing on this page.

Is the eCFR API ready for AI agents?

eCFR has a Kin Score of 23.8 out of 100 (emerging) and an Agent Readiness score of 26.4 (agent-aware), scored by API Evangelist on 2026-11-06.

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