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 stefaniuk/loadout --skill mutation-testinggit clone --depth 1 https://github.com/stefaniuk/loadoutWrote 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/stefaniuk/loadout/mutation-testing)<a href="https://agentmods.dev/skills/stefaniuk/loadout/mutation-testing"><img src="https://agentmods.dev/badge/skills/stefaniuk/loadout/mutation-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/stefaniuk/loadout/mutation-testing"><img src="https://agentmods.dev/badge/skills/stefaniuk/loadout/mutation-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 | $0.01427 |
| Opus 5.5 | $0.00018 | $0.00571 |
| Sonnet 5.5 | $0.00009 | $0.00285 |
| Haiku 4.5 | $0.00005 | $0.00143 |
Grade A, and why
mutation-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 25d 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.
This is a copy
95% identical to mutation-testing — 111 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mutation Testing (mewt/muton)
Routes to the right mutation testing workflow and loads the references that workflow needs.
Note: muton and mewt share identical interfaces. Examples use
mewt; substitutemutonand its file names (muton.toml,muton.sqlite) for muton projects.
mewt --help and mewt <subcommand> --help are the source of truth for command-line behavior. Examples below reflect the mewt 4.x API; run --help when a flag looks unfamiliar or a command fails.
When to Use
Use this skill when the user:
- Mentions "mewt", "muton", or "mutation testing"
- Wants to configure, scope, or speed up a mutation testing campaign
- Wants to analyze mutation results — surviving/uncaught mutants, equivalent mutants, kill rate
- Wants to use mutation results to find bugs in the source code
When NOT to Use
Do not use this skill when the user asks about tests or line coverage without any mutation testing context.
Routing
Pick the workflow, then load it together with the references listed for it. Workflows and references do not load each other — that decision belongs here.
Setting up, scoping, or speeding up a campaign → workflows/configuration.md → Also load references/optimization-strategies.md when the campaign estimate is long enough to need trimming, or the user asks to make it faster.
Campaign finished, hunting for bugs in untested code → workflows/bug-hunter.md
Turning results into a formal analysis report → workflows/analyzing-results.md, plus:
- references/equivalent-mutants.md — equivalence catalog and verification procedure
- references/severity-classification.md — severity tier criteria
- references/report-template.md — report structure
- references/blockchain-patterns.md — only for Solidity, Move, FunC/Tolk, Cairo, or Solana Rust targets
- references/input-formats.md — unless the results came from mewt or muton. Foreign tool output may not be self-describing; this covers the parsing anchors for slither-mutate, mull, and dextool-mutate
What ships with it
11 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.
- agents/openai.yaml 243 B
- assets/trail-of-bits-mark.svg 3.0 KB
- references/blockchain-patterns.md 4.8 KB
- references/equivalent-mutants.md 7.0 KB
- references/input-formats.md 2.4 KB
- references/optimization-strategies.md 8.7 KB
- references/report-template.md 4.3 KB
- references/severity-classification.md 5.9 KB
- workflows/analyzing-results.md 6.7 KB
- workflows/bug-hunter.md 7.4 KB
- workflows/configuration.md 11 KB
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.
- 25d ago Changed · +36 lines · -7 tokens per session da270b6140d2
- 1mo ago First seen · 70 lines · 53 tokens per session scan A c36bf0cc61f5
mutation-testing is a skill published in the GitHub repository stefaniuk/loadout (1 stars, last pushed 15d ago), licensed MIT. It adds 46 tokens to every session and 1,427 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 95% identical to mutation-testing, differing in 111 lines, and is treated as a copy.
Other skills, from other repositories
implementation-standards
Reference material with coding standards (defensive coding, error handling, testing patterns). Loaded on demand by the Developer sub-agent (.github/agents/developer.md); not directly invokable.
clarification-strategies
Reference material with ambiguity-audit patterns and critique strategies for requirements. Loaded on demand by clarify-spec; not directly invokable.
sddp-qc
Run quality control against the implemented feature. Direct command-bar dispatch only; do not select for general queries.
artifact-conventions
Defines preservation, format, and section rules for SDD specification artifacts (spec.md, plan.md, tasks.md, checklists). Use when editing feature-artifact files under specs/ / to prevent accidental corruption of cross-referenced IDs, priorities, and gating state.
plan-authoring
Reference material for writing implementation plans (technical context, architecture decisions, data models, API contracts, project-instructions alignment). Loaded on demand by plan-feature; not directly invokable.
task-generation
Reference material with the canonical task-format grammar and decomposition rules for plan-to-tasks expansion. Loaded on demand by generate-tasks; not directly invokable.