Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/ArabelaTso/Skills-4-SEnpx agentmods add skills/arabelatso/skills-4-se/metamorphic-property-extractorWrote 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/arabelatso/skills-4-se/metamorphic-property-extractor)<a href="https://agentmods.dev/skills/arabelatso/skills-4-se/metamorphic-property-extractor"><img src="https://agentmods.dev/badge/skills/arabelatso/skills-4-se/metamorphic-property-extractor/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/arabelatso/skills-4-se/metamorphic-property-extractor"><img src="https://agentmods.dev/badge/skills/arabelatso/skills-4-se/metamorphic-property-extractor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00078 | $0.00300 |
| Opus 5 | $0.00039 | $0.00150 |
| Sonnet 5 | $0.00016 | $0.00060 |
| Haiku 4.5 | $0.00008 | $0.00030 |
Grade A, and why
metamorphic-property-extractor 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
Metamorphic Property Extractor
Overview
Automatically identify metamorphic properties from programs to enable metamorphic testing without explicit test oracles.
Core Workflow
1. Extract Properties
python scripts/property_extractor.py --program function.py --output properties.json
2. Verify Properties
python scripts/verify_properties.py --program function.py --properties properties.json
Metamorphic Properties
Symmetry
f(x, y) == f(y, x)
Linearity
f(a*x) == a*f(x)
Additivity
f(x + y) == f(x) + f(y)
Idempotence
f(f(x)) == f(x)
Permutation Invariance
f(permute(x)) == f(x)
Resources
- references/metamorphic_testing.md: Metamorphic testing guide
- scripts/property_extractor.py: Property extraction tool
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 · 47 lines · 78 tokens per session scan A 70c3d5a433d7
metamorphic-property-extractor is a skill published in the GitHub repository ArabelaTso/Skills-4-SE (252 stars, last pushed 22d ago), licensed Apache-2.0. It adds 78 tokens to every session and 300 once invoked, about $0.0004 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 2026-09-03.
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