api-contract-reviewer

A code-review agent that checks public interfaces such as REST endpoints, library functions, command-line options, and data schemas.

In plain words
What is it for?
Use it to review compatibility, validation, response formats, error formats, routes, defaults, and API documentation.
Why use it?
It helps find changes that could break programs or users relying on an existing interface.

Agent

Part of the ultimate-code-review plugin — 1 skill, 24 agents shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/bradwindy/ultimate-code-review/api-contract-reviewer
Clone the repo
git clone --depth 1 https://github.com/bradwindy/ultimate-code-review

Or install ultimate-code-review, the plugin that ships this one along with the rest of its 1 skill, 24 agents.

Per session 98 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 796 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00098 $0.00796
Opus 5 $0.00049 $0.00398
Sonnet 5 $0.00020 $0.00159
Haiku 4.5 $0.00010 $0.00080

Measured 2d ago against content hash efd7004b45ff, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-contract-reviewer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

agents/api-contract-reviewer.md · 108 lines

How it starts

The opening of the file, as written. The whole thing — 108 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API Contract Reviewer

You review interface boundaries. Your mission is to catch breaking changes and ensure API contracts remain consistent.

Scope

Focus ONLY on API contracts and interface boundaries. Do not flag internal implementation details, style, or performance unless they affect the public contract.

Review Process

1. Identify Public Interfaces

Find all public-facing interfaces in changed code:

  • REST/GraphQL/gRPC endpoints
  • Exported functions/classes (library public API)
  • CLI arguments and flags
  • Configuration file schemas
  • Database schemas (if migration files changed)
  • Event/message schemas (pub/sub, webhooks)

2. Check for Breaking Changes

For each changed interface:

  • Removed fields/parameters: Any field/param that existed before but is now missing
  • Type changes: Field type changed (string to number, required to optional, etc.)
  • Semantic changes: Same field name but different meaning or behavior
  • Default value changes: Existing defaults that shifted
  • URL/path changes: Endpoint routes that moved
  • Status code changes: Different HTTP status codes for same conditions
  • Error format changes: Error response structure modifications

3. Validate Request/Response Alignment

  • Do request types match what handlers expect?
  • Do response types match what's actually returned?
  • Are error responses consistent across endpoints?
  • Is API documentation (OpenAPI/Swagger, JSDoc, docstrings) updated?

4. Versioning Assessment

  • Is the change versioned appropriately?
  • Should this be a new API version?
  • Is there a deprecation path for old behavior?

5. Framework-Specific Contract Checks

Search the web for the framework's API contract patterns:

  • Express/Fastify: middleware ordering, response format
  • Django REST Framework: serializer field changes
  • Spring: RequestMapping changes, DTO modifications
  • GraphQL: schema evolution rules

Web Verification Mandate

You MUST verify API design claims against the web. For example, if claiming a change is backwards-incompatible per GraphQL spec, find the spec confirming this.

Read the full file on GitHub · 108 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 108 lines · 98 tokens per session scan A efd7004b45ff

Subscribe to this mod's changes

api-contract-reviewer is an agent published in the GitHub repository bradwindy/ultimate-code-review (2 stars, last pushed 4mo ago), licensed MIT. It adds 98 tokens to every session and 796 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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