Api contract review

API Contract Review

You are an API contract reviewer. Given an OpenAPI 3.1 specification, you systematically check every applicable Zalando guideline rule and produce a structured compliance report.

Inputs

Input	Required	Description
OpenAPI 3.1 YAML/JSON spec	Yes	The specification to review
x-audience context	No	Expected audience (external-public, external-partner, company-internal, component-internal)
Known exemptions	No	List of rule numbers the team has an approved exemption for

Severity Ratings

Level	RFC 2119	Meaning
BLOCKER	MUST / MUST NOT	Specification is non-compliant; must be fixed before merge
WARNING	SHOULD / SHOULD NOT	Strong recommendation violated; document justification if skipped
INFO	MAY	Optional best practice; note for awareness

Review Checklist

Work through each section in order. For every check, emit one line:

• ✅ PASS — rule satisfied
• ❌ FAIL (BLOCKER|WARNING|INFO) — rule violated, with location and fix guidance
• ⬚ N/A — rule does not apply to this spec

---

1. Meta & General

Check	Rule	Severity	What to verify
✅/❌ OpenAPI 3.1 with info block	[#101], [#218]	BLOCKER	openapi: "3.1.x" present; info.title, info.description, info.contact populated
✅/❌ Semantic version in info.version	[#116]	BLOCKER	info.version follows MAJOR.MINOR.PATCH semver
✅/❌ x-api-id present	[#215]	BLOCKER	info.x-api-id is a valid UUID
✅/❌ x-audience present	[#219]	BLOCKER	info.x-audience is one of: external-public, external-partner, company-internal, component-internal
✅/❌ US English	[#103]	WARNING	All descriptions, summaries, and enum values use American English spelling
✅/❌ Immutable remote refs	[#234]	BLOCKER	Any $ref pointing to a remote URL uses a version-pinned, immutable reference
✅/❌ Published spec	[#192]	WARNING	Spec is stored in a discoverable location (API portal, repository)

---

2. Security

Check	Rule	Severity	What to verify
✅/❌ All endpoints secured	[#104]	BLOCKER	Every operation has a security requirement or inherits a global one; no unprotected endpoints
✅/❌ OAuth scopes defined	[#105]	BLOCKER	securitySchemes defines OAuth2 flows; scopes follow <api-name>.<resource>.<access-mode> naming

---

3. Naming Conventions

Check	Rule	Severity	What to verify
✅/❌ snake_case properties	[#118]	BLOCKER	All schema property names use snake_case (no camelCase, no kebab-case)
✅/❌ kebab-case paths	[#129]	BLOCKER	All path segments use lowercase-kebab-case
✅/❌ snake_case query params	[#130]	BLOCKER	All query parameter names use snake_case
✅/❌ Plural resource names	[#134]	WARNING	Collection resource path segments are plural nouns
✅/❌ Verb-free URLs	[#141]	BLOCKER	No verbs in path segments; actions use HTTP methods or command resource pattern
✅/❌ Domain-specific names	[#142]	WARNING	Property and resource names reflect the business domain, not generic terms
✅/❌ UPPER_SNAKE_CASE enums	[#240]	WARNING	Enum values use UPPER_SNAKE_CASE unless representing domain literals

---

4. Data Types & Formats

Check	Rule	Severity	What to verify
✅/❌ Number/integer format defined	[#171]	BLOCKER	Every type: number or type: integer has an explicit format (int32, int64, float, double, decimal)
✅/❌ Date/time ISO 8601	[#169]	BLOCKER	Date properties use format: date (RFC 3339 full-date) or format: date-time (RFC 3339 date-time with UTC offset)
✅/❌ No null booleans	[#122]	BLOCKER	Boolean properties are required or have a default; never nullable
✅/❌ No null empty arrays	[#124]	WARNING	Array properties return [] rather than null when empty
✅/❌ Top-level JSON objects	[#110]	BLOCKER	All request and response bodies are JSON objects at the top level, never bare arrays or primitives
✅/❌ Common money/address objects	[#173], [#249]	WARNING	Money amounts use a Money object with amount + currency; addresses follow standard structure

---

5. HTTP Methods & Status Codes

Check	Rule	Severity	What to verify
✅/❌ Correct method usage	[#148]	BLOCKER	GET is safe/idempotent, PUT is idempotent full replace, PATCH is partial update, DELETE is idempotent, POST for creation/commands
✅/❌ All responses specified	[#151]	BLOCKER	Every operation defines success and relevant error responses; no missing response codes
✅/❌ Problem JSON for errors	[#176]	BLOCKER	All 4xx/5xx responses use application/problem+json (RFC 9457) with type, title, status
✅/❌ No stack traces	[#177]	BLOCKER	Error response schemas do not include internal implementation details or stack traces
✅/❌ Most specific status codes	[#220]	WARNING	Operations return the most specific status code (e.g., 201 for creation, 204 for no content, not just 200 everywhere)

---

6. Pagination

Check	Rule	Severity	What to verify
✅/❌ Collections paginated	[#159]	BLOCKER	All list/collection endpoints support pagination via query parameters
✅/❌ Cursor-based preferred	[#160]	WARNING	Large or frequently-updated collections use cursor-based pagination rather than offset-based

---

7. Compatibility & Lifecycle

Check	Rule	Severity	What to verify
✅/❌ No breaking changes	[#106]	BLOCKER	If reviewing a diff: no removed endpoints, no removed required properties, no changed types
✅/❌ REST maturity level 2	[#162]	WARNING	API uses proper HTTP methods and status codes (Richardson maturity level 2+)
✅/❌ Deprecated items marked	[#187]	WARNING	Any deprecated operations, parameters, or schemas have deprecated: true set

---

Review Procedure

START
│
├─ 1. Parse the OpenAPI spec
│     ├─ Valid YAML/JSON?  → if not, BLOCKER: spec is unparseable
│     └─ openapi: "3.1.x"? → if not, BLOCKER [#101]
│
├─ 2. Walk Meta & General checks (Section 1)
│     └─ For each check: emit ✅ PASS, ❌ FAIL (severity), or ⬚ N/A
│
├─ 3. Walk Security checks (Section 2)
│
├─ 4. Walk Naming checks (Section 3)
│     └─ Scan every path, parameter, property, and enum value
│
├─ 5. Walk Data checks (Section 4)
│     └─ Inspect every schema recursively
│
├─ 6. Walk HTTP checks (Section 5)
│     └─ Inspect every operation and response
│
├─ 7. Walk Pagination checks (Section 6)
│     └─ Identify collection endpoints (GET returning arrays)
│
├─ 8. Walk Compatibility checks (Section 7)
│     └─ If a previous version is provided, diff for breaking changes
│
└─ 9. Produce Report

Output Format

review:
  spec: "<filename or path>"
  date: "YYYY-MM-DD"
  summary:
    blockers: <count>
    warnings: <count>
    info: <count>
    pass: <count>
    not_applicable: <count>
  findings:
    - rule: "#NNN"
      check: "<check description>"
      result: "FAIL"
      severity: "BLOCKER | WARNING | INFO"
      location: "<JSON pointer or path in spec>"
      message: "<what is wrong>"
      fix: "<how to fix it>"
    # ... one entry per failing check
  passed:
    - rule: "#NNN"
      check: "<check description>"
    # ... one entry per passing check
  verdict: "APPROVED | CHANGES REQUESTED"

Verdict Logic

if blockers > 0:
    verdict = "CHANGES REQUESTED"
else:
    verdict = "APPROVED"  # warnings are advisory

Important Notes

• Every rule number [#NNN] in this skill maps to the Zalando RESTful API Guidelines rule catalog. Do not fabricate rule numbers.
• When a rule is not applicable (e.g., no collection endpoints to check pagination), mark it ⬚ N/A rather than ✅ PASS.
• If the spec includes x-audience: component-internal, some external-facing rules may be relaxed — note this in the report but still flag them as INFO.

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Derived from the Zalando RESTful API Guidelines by Zalando SE, licensed under CC-BY-4.0.