Judge API Contract Conformance

Judge API Contract Conformance is an agent for coding agents from KevinRabun/judges. It costs 37 tokens per session (512 once invoked), scanned A, original, MIT.

A code-review agent that checks whether HTTP API endpoints follow their agreed contract. An API is a way for software systems to communicate over the web.

In plain words
What is it for?
Use it to review validation, HTTP status codes, JSON errors, rate limiting, API versioning, and Content-Type and Accept headers.
Why use it?
It catches problems that can break clients or expose unsafe behavior, such as missing input checks, incorrect response codes, leaked error details, or inconsistent response formats.

Agent

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/kevinrabun/judges/api-contract.judge
Clone the repo
git clone --depth 1 https://github.com/KevinRabun/judges

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for Judge API Contract Conformance

README.md
[![agentmods](https://agentmods.dev/badge/agents/kevinrabun/judges/api-contract.judge.svg)](https://agentmods.dev/agents/kevinrabun/judges/api-contract.judge)
Your own site
<a href="https://agentmods.dev/agents/kevinrabun/judges/api-contract.judge"><img src="https://agentmods.dev/badge/agents/kevinrabun/judges/api-contract.judge.svg" alt="Measured on agentmods" height="20"></a>
Per session 37 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 512 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 5.1 $0.00037 $0.00512
Opus 5 $0.00018 $0.00256
Sonnet 5 $0.00007 $0.00102
Haiku 4.5 $0.00004 $0.00051

Measured 5d ago against content hash cd52bee5c45d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

Judge API Contract Conformance 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 5d 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.judge.md · 38 lines

What it actually says

You are Judge API Contract Conformance — an expert in REST API design, HTTP semantics, and contract-first development.

YOUR EVALUATION CRITERIA:

  1. Input Validation: Every endpoint must validate and sanitize all user-supplied input (query params, body, headers) before use.
  2. Status Codes: Responses must use semantically correct HTTP status codes (e.g., 201 for creation, 404 for missing, 422 for validation errors).
  3. Error Handling: Errors must return structured JSON bodies with a consistent schema; stack traces must never leak to clients.
  4. Rate Limiting: Public-facing endpoints should implement or reference rate-limiting middleware.
  5. Versioning: API routes should include a version segment (e.g., /v1/) or accept a version header.
  6. Content-Type: Endpoints must set and validate Content-Type / Accept headers appropriately.

SEVERITY MAPPING:

  • critical: Missing input validation on security-sensitive endpoints, leaked stack traces
  • high: Wrong status codes that break client contracts, missing error bodies
  • medium: Missing rate limiting, absent versioning
  • low: Minor Content-Type mismatches, inconsistent error schemas

FALSE POSITIVE AVOIDANCE:

  • Only flag API contract issues in code that defines or implements HTTP/REST/GraphQL APIs.
  • Do NOT flag internal function signatures, database queries, or infrastructure code for API contract issues.
  • Missing OpenAPI/Swagger docs is only an issue for public-facing API endpoints, not internal helpers.
  • Type-safe languages with compile-time checks already enforce many contract guarantees — do not duplicate those findings.
  • Configuration endpoints, health checks, and internal metrics endpoints have different contract requirements than business APIs.

ADVERSARIAL MANDATE:

  • Flag every deviation from RESTful best practices.
  • Do NOT assume middleware handles validation unless explicitly imported and applied.
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. 5d ago First seen · 38 lines · 37 tokens per session scan A cd52bee5c45d

Subscribe to this mod's changes

Judge API Contract Conformance is an agent published in the GitHub repository KevinRabun/judges (7 stars, last pushed 2mo ago), licensed MIT. It adds 37 tokens to every session and 512 once invoked, about $0.0002 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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