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 Claritune/mutantx --skill mx-validategit clone --depth 1 https://github.com/Claritune/mutantxWrote 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/claritune/mutantx/mx-validate)<a href="https://agentmods.dev/skills/claritune/mutantx/mx-validate"><img src="https://agentmods.dev/badge/skills/claritune/mutantx/mx-validate/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/claritune/mutantx/mx-validate"><img src="https://agentmods.dev/badge/skills/claritune/mutantx/mx-validate.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 | $0.00021 | $0.00649 |
| Opus 5.5 | $0.00008 | $0.00260 |
| Sonnet 5.5 | $0.00004 | $0.00130 |
| Haiku 4.5 | $0.00002 | $0.00065 |
Grade A, and why
mx-validate 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 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.
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 — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MutantX — Mutation Validation (AI Review)
You are the validation phase of a mutation testing engine. Your job is to review mutants that were flagged as needs-review by the deterministic validator.
These are mutants whose source file changed since generation, but whose patch still applies cleanly. The patch is syntactically applicable, but you need to determine if the mutation is still semantically meaningful.
When This Runs
This skill is invoked after mx-validate.py has already run and marked some mutants as needs-review. If no mutants have that status, tell the user there's nothing to review and exit.
Workflow
1. Read the manifest
Read .mutants/manifest.json. Find all mutants with status: "needs-review".
If there are none, tell the user: "No mutants need review. All are either valid or stale."
2. For each needs-review mutant
Read the mutant's patch file from .mutants/patches/NNN.patch.
Read the current version of the source file the mutant targets.
Evaluate:
-
Does the mutation still target the same logical code? The patch applies, but did the surrounding code change in a way that shifts what the mutation actually does? For example, if the mutation changes a return value but a new early return was added above it, the mutated line may now be unreachable.
-
Is the mutation still semantically different from the original? Could the file change have made this mutation equivalent (no observable behavior difference)?
-
Is the mutation still a realistic bug? If the code around it changed significantly, the mutation might no longer represent a plausible developer mistake.
3. Decide: promote or discard
For each mutant, set the status:
-
pending— the mutation is still valid. The file changed but the mutation still targets the same logic, is semantically different, and represents a realistic bug. Updatevalidation_noteto briefly explain why it's still valid. -
stale— the mutation is no longer meaningful. Updatevalidation_noteto explain why (e.g., "Mutated line is now unreachable due to new guard clause at line 42", "Mutation is now equivalent — return value is immediately overwritten").
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 · 68 lines · 21 tokens per session scan A 6419dc1c74cf
mx-validate is a skill published in the GitHub repository Claritune/mutantx (2 stars, last pushed 2mo ago), licensed MIT. It adds 21 tokens to every session and 649 once invoked, about $0.0001 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 2026-08-31.
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