restful-hateoas

Community RESTful HATEOAS Best Practices

Comprehensive guide to building REST APIs that reach the Glory of REST (Richardson Maturity Level 3) in Ruby on Rails. Contains 47 rules across 9 categories, ordered by the request/response lifecycle — from resource URI design through hypermedia link relations to API evolution.

When to Apply

Reference these guidelines when:

• Designing new REST API endpoints and resource URIs
• Adding hypermedia controls (_links, affordances) to API responses
• Implementing content negotiation with HAL, JSON:API, or vendor media types
• Building paginated, filterable, sortable collection endpoints
• Reviewing APIs for proper HTTP method semantics and status codes
• Evolving APIs without breaking existing clients

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	Resource Modeling	CRITICAL	res-
2	HTTP Method Semantics	CRITICAL	http-
3	Hypermedia & Link Relations	CRITICAL	link-
4	Status Codes & Response Headers	HIGH	status-
5	Content Negotiation & Media Types	HIGH	media-
6	Collection Patterns	MEDIUM-HIGH	coll-
7	Error Semantics	MEDIUM	err-
8	Caching & Conditional Requests	MEDIUM	cache-
9	API Evolution	LOW-MEDIUM	evolve-

Quick Reference

1. Resource Modeling (CRITICAL)

• res-noun-based-uris - URIs must be nouns, not verbs
• res-plural-collection-uris - Always use plural nouns for collections
• res-limit-nesting-depth - Limit nested resources to max 2 levels
• res-model-business-entities - Model business entities, not database tables
• res-use-consistent-identifiers - Use opaque identifiers, never auto-increment IDs
• res-sub-resources-for-relationships - Express relationships as sub-resources

2. HTTP Method Semantics (CRITICAL)

• http-get-must-be-safe - Keep GET requests free of side effects
• http-post-for-creation - Return 201 Created with Location header from POST
• http-put-for-full-replacement - Use PUT only for full resource replacement
• http-patch-for-partial-updates - PATCH for partial updates with merge semantics
• http-delete-is-idempotent - Ensure DELETE is idempotent
• http-head-for-metadata - Use HEAD for metadata without body transfer
• http-idempotency-key - Use idempotency keys for safe POST retries

3. Hypermedia & Link Relations (CRITICAL)

• link-self-link-every-resource - Include a self link in every resource
• link-related-resource-links - Link to related resources instead of foreign keys
• link-action-affordances - Expose available actions as conditional links
• link-standard-relation-types - Use IANA-registered link relation types
• link-entry-point - Provide a root API entry point
• link-pagination-links - Use hypermedia links for pagination
• link-embedded-vs-linked - Choose between embedding and linking

4. Status Codes & Response Headers (HIGH)

• status-201-with-location - Return 201 Created with Location header
• status-204-for-no-content - Return 204 No Content for empty responses
• status-409-for-conflicts - Return 409 Conflict for state conflicts
• status-202-for-async - Return 202 Accepted for async operations
• status-allow-header-on-405 - Return 405 with Allow header for wrong methods
• status-rate-limit-headers - Include rate limit headers in API responses

5. Content Negotiation & Media Types (HIGH)

• media-accept-header-negotiation - Respect the Accept header for content negotiation
• media-content-type-in-responses - Set the correct Content-Type in every response
• media-vendor-media-types - Use vendor media types for API versioning
• media-406-for-unsupported-types - Return 406 for unsupported media types

6. Collection Patterns (MEDIUM-HIGH)

• coll-cursor-pagination - Use cursor-based pagination instead of offset
• coll-link-header-pagination - Include pagination links in body and Link header
• coll-filtering-via-query-params - Support filtering via typed query parameters
• coll-sorting-convention - Support sorting with a standardized sort parameter
• coll-field-selection - Support sparse fieldsets via fields parameter

7. Error Semantics (MEDIUM)

• err-problem-details - Use Problem Details (RFC 9457) for errors
• err-validation-errors - Return structured validation errors
• err-error-links - Include recovery links in error responses
• err-machine-readable-codes - Use machine-readable error codes
• err-auth-error-codes - Distinguish 401 Unauthorized from 403 Forbidden

8. Caching & Conditional Requests (MEDIUM)

• cache-etag-conditional-get - Use ETags with stale? for conditional GET
• cache-last-modified - Set Last-Modified for time-based validation
• cache-cache-control-headers - Set explicit Cache-Control headers
• cache-vary-header - Include Vary header for content-dependent caching

9. API Evolution (LOW-MEDIUM)

• evolve-additive-changes-only - Make only additive changes to responses
• evolve-deprecation-headers - Use Deprecation and Sunset headers
• evolve-hateoas-reduces-versioning - Leverage HATEOAS to eliminate URL versioning

How to Use

Read individual reference files for detailed explanations and code examples:

• Section definitions - Category structure and impact levels
• Rule template - Template for adding new rules

Reference Files

File	Description
references/_sections.md	Category definitions and ordering
assets/templates/_template.md	Template for new rules
metadata.json	Version and reference information