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.
npx skills add JansenAnalytics/claudex --skill api-criticgit clone --depth 1 https://github.com/JansenAnalytics/claudexWrote 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.
[](https://agentmods.dev/skills/jansenanalytics/claudex/api-critic)<a href="https://agentmods.dev/skills/jansenanalytics/claudex/api-critic"><img src="https://agentmods.dev/badge/skills/jansenanalytics/claudex/api-critic/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/jansenanalytics/claudex/api-critic"><img src="https://agentmods.dev/badge/skills/jansenanalytics/claudex/api-critic.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00072 | $0.00842 |
| Opus 5.5 | $0.00029 | $0.00337 |
| Sonnet 5.5 | $0.00014 | $0.00168 |
| Haiku 4.5 | $0.00007 | $0.00084 |
Grade A, and why
api-critic scanned grade A with 1 finding 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 1mo 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.
Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
None. Uses only Node.js built-in modules (http, https, fs, path, url, child_process). How it starts
The opening of the file, as written. The whole thing — 99 lines — stays where its author put it; the contents beside it link to each section on GitHub.
api-critic — Autonomous API Testing & Evaluation
Like design-critic but for backends. Tests any REST API for correctness, security, performance, error handling, and standards compliance.
Quick Start
api-critic https://jsonplaceholder.typicode.com
api-critic http://localhost:3000 --auth "Bearer token" --full
api-critic http://localhost:3000 --quick
api-critic http://localhost:3000 --compare /tmp/api-critic-previous
Options
| Flag | Description |
|---|---|
--endpoints FILE |
Manual route list (JSON: [{method, path, body?}]) |
--auth "Bearer x" |
Authorization header for all requests |
--timeout MS |
Request timeout (default: 10000) |
--quick |
Skip edge cases (SQL injection, XSS, oversized payload) |
--full |
Run everything including extended probes |
--compare DIR |
Compare with previous run's output directory |
--out-dir DIR |
Output directory (default: /tmp/api-critic-TIMESTAMP) |
What It Tests
Correctness
- Happy path (valid requests → 2xx)
- JSON validity, schema types
- Status code correctness (201 for POST, 204 for DELETE)
Security
- CORS wildcard detection
- Auth bypass (requests without auth header)
- Malformed token acceptance
- SQL injection strings in query params
- XSS reflection in responses
- Mass assignment (extra unknown fields accepted)
Performance
- Response time (>500ms warning, >2000ms critical)
Error Handling
- Empty body, null values → should get 4xx not 5xx
- Wrong Content-Type handling
- Oversized payload (1MB)
Standards
- Content-Type headers present
- Cache headers on GET responses
- 405 for wrong HTTP methods
- Pagination support detection
Pipeline
- discover.cjs — Finds endpoints (OpenAPI spec, common paths, CRUD inference)
- probe.cjs — Runs all tests against each endpoint
- report.cjs — Generates scored report (0-100, grade A-F)
Output
discovered-endpoints.json— Found endpointsprobe-results.json— Raw test resultsapi-critic-report.md— Human-readable reportapi-critic-report.json— Machine-readable summary
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 1mo ago First seen · 99 lines · 72 tokens per session scan A e0722872e41f
api-critic is a skill published in the GitHub repository JansenAnalytics/claudex (5 stars, last pushed 4mo ago), licensed MIT. It adds 72 tokens to every session and 842 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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