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 cowwoc/cat --skill render-diffgit clone --depth 1 https://github.com/cowwoc/catWrote 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/cowwoc/cat/render-diff)<a href="https://agentmods.dev/skills/cowwoc/cat/render-diff"><img src="https://agentmods.dev/badge/skills/cowwoc/cat/render-diff/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/cowwoc/cat/render-diff"><img src="https://agentmods.dev/badge/skills/cowwoc/cat/render-diff.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 | $0.00048 | $0.01755 |
| Opus 5.5 | $0.00019 | $0.00702 |
| Sonnet 5.5 | $0.00010 | $0.00351 |
| Haiku 4.5 | $0.00005 | $0.00176 |
Grade A, and why
render-diff 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.
The source is not reproduced here
A licence we could not identify
The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.
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 · 213 lines · 48 tokens per session scan A 87eebbb77234
render-diff is a skill published in the GitHub repository cowwoc/cat (101 stars, last pushed 2mo ago), with no licence file. It adds 48 tokens to every session and 1,755 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 2026-08-30.
Other skills, from other repositories
gsd-code-review
Review source files changed during a phase for bugs, security issues, and code quality problems.
gsd-review
Request cross-AI peer review of phase plans from external AI CLIs.
gsd-ns-review
Invoke this Pi skill with /skill:gsd-ns-review.
gsd-pr-branch
Create a clean PR branch by filtering out .planning/ commits — ready for code review.
best-practices
Apply modern web development best practices for security, compatibility, and code quality. Use when asked to "apply best practices", "security audit", "modernize code", "code quality review", or "check for vulnerabilities".
review
Review code changes for security, performance, bugs, and quality. Reviews staged changes, unstaged changes, specific commits, or PR-ready diffs.