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 HoangNguyen0403/agent-skills-standard --skill quality-engineering-api-fuzz-testinggit clone --depth 1 https://github.com/HoangNguyen0403/agent-skills-standardWrote 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/hoangnguyen0403/agent-skills-standard/quality-engineering-api-fuzz-testing)<a href="https://agentmods.dev/skills/hoangnguyen0403/agent-skills-standard/quality-engineering-api-fuzz-testing"><img src="https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/quality-engineering-api-fuzz-testing/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/hoangnguyen0403/agent-skills-standard/quality-engineering-api-fuzz-testing"><img src="https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/quality-engineering-api-fuzz-testing.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 | $0.00046 | $0.01121 |
| Opus 5.5 | $0.00018 | $0.00448 |
| Sonnet 5.5 | $0.00009 | $0.00224 |
| Haiku 4.5 | $0.00005 | $0.00112 |
Grade A, and why
quality-engineering-api-fuzz-testing 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 today.
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.
How it starts
The opening of the file, as written. The whole thing — 63 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Quality Engineering: API Fuzz and Security Testing
Priority: P0 (CRITICAL)
Input
API operation contract (OpenAPI/DTO/schema), target endpoint, expected invariants, and authorization status. Purpose is fuzz or security (lane: api).
Core Rules
[API-FUZZ-01]Discovery vs Robustness: Distinguish content discovery (wordlist bruteforce) from structured fuzz testing. Fuzzing validates contract violations, unexpected 500s, unauthorized state changes, and resource exhaustion under malformed inputs.[API-FUZZ-02]Four Contract-Derived Oracles: Assert 4 invariants against approved operation contracts:- Crash Resilience: No unhandled 500/502/504 errors; invalid inputs return contract-approved 4xx; valid boundary cases return contract-approved 2xx.
- Contract Conformance: Payloads match approved success/error schemas without stack traces or path leaks.
- State & Isolation: No unauthorized state mutation, unpermitted field updates, or cross-tenant leakage.
- Resource & Containment: Client enforces containment deadline with cancellation/drain; product latency evaluated against approved contract SLOs (never invent universal thresholds). Client safety ceilings (timeout, bytes, depth) are own-execution bounds, not product PASS criteria; any numeric fixture objective must be labeled synthetic and replaced with the approved objective before execution.
[API-FUZZ-03]Deterministic Seeds & Minimization: Runs must record PRNG seeds. Failing inputs must be minimized (shrunk) to the smallest reproducing payload with explicit reproduction commands. Discovery runs with shrinking enabled; shrink replays count against the finite budget. Disabling shrinking is permitted only when replaying an already minimized seed/input, never for discovery.[API-FUZZ-04]Regression Promotion: Minimized distinct failures must be promoted to permanent deterministic regression tests (lane: api, purpose:regression).[API-FUZZ-05]Real Guards for Security Proof (AC-13): Authorization tests must exercise real guards and permission filters with synthetic tenant/role personas. Bypassed guards (canActivate: () => true) cannot serve as security proof.[API-FUZZ-06]Authorization & Safety Gate (AC-15,C4): Active dynamic fuzzing requires explicit target authorization, isolated synthetic environments, finite generation/payload byte/depth caps, and active cancellation/drain on timeout. If authorization or caps are unconfirmed, mark dependent executionBLOCKEDwhile continuing offline harness/case planning. Agents cannot self-authorize.
What ships with it
3 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.
- today First seen · 63 lines · 46 tokens per session scan A ffbee5a3c107
quality-engineering-api-fuzz-testing is a skill published in the GitHub repository HoangNguyen0403/agent-skills-standard (582 stars, last pushed today), licensed MIT. It adds 46 tokens to every session and 1,121 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-10-28.
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