Borrowing it
Nothing to install: this file belongs to Grinv/anilist-mcp-server. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/Grinv/anilist-mcp-server/main/.agents/skills/mutation-test-safety/SKILL.mdgit clone --depth 1 https://github.com/Grinv/anilist-mcp-serverWrote 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/grinv/anilist-mcp-server/mutation-test-safety)<a href="https://agentmods.dev/skills/grinv/anilist-mcp-server/mutation-test-safety"><img src="https://agentmods.dev/badge/skills/grinv/anilist-mcp-server/mutation-test-safety/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/grinv/anilist-mcp-server/mutation-test-safety"><img src="https://agentmods.dev/badge/skills/grinv/anilist-mcp-server/mutation-test-safety.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 | $0.00051 | $0.00360 |
| Opus 5 | $0.00026 | $0.00180 |
| Sonnet 5 | $0.00010 | $0.00072 |
| Haiku 4.5 | $0.00005 | $0.00036 |
Grade A, and why
mutation-test-safety 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 9d 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.
What it actually says
Mutation testing safety contract
Applies to any mutation tool (add/update/remove/delete/post/toggle_follow/ toggle_favourite/etc.) once the user has given explicit go-ahead to test it against a real account. For every mutation call:
- Capture the exact pre-state first (via the matching read tool) — not just an assumption of what it probably is. A target with no existing state has a clear pre-state too: "absent."
- Make the smallest possible change that still exercises the behavior (e.g. one field, not a full rewrite).
- Verify the change landed by re-fetching via a read tool — a mutation's own echoed response is not always trustworthy (some tools have historically omitted fields they actually changed).
- Revert to the captured pre-state immediately, in the same turn, and verify the revert too. Don't batch several mutations and revert at the end — revert each one before moving to the next unrelated test.
- Never leave the target in a different state than you found it, even if a step errors partway through — check and clean up regardless.
- Never touch an uninvolved third party. Self-targeted mutations (a self-message, a self-created and immediately-deleted test post/ thread/comment) are fine; acting on a random other real user/account is not.
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.
- 9d ago First seen · 29 lines · 51 tokens per session scan A 83ef5cf8013f
mutation-test-safety is a skill published in the GitHub repository Grinv/anilist-mcp-server (1 stars, last pushed 16d ago), licensed MIT. It adds 51 tokens to every session and 360 once invoked, about $0.0003 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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add-test
Scaffold a test file for an existing tool, resource, or service. Use when the user asks to add tests, improve coverage, or when a definition exists without a matching test file.
live-audit
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prompt-check
Live-test every MCP Prompt in src/tools/prompts.ts through the real MCP protocol (not a static read) across every argument combination. Use when a prompt is added or its argument-handling logic changes, or as part of a live-audit pass.
verify-cli
Run smoke tests against the mpak CLI to verify all commands work correctly before publishing a new release.