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 shennawardana23/skillme --skill best-practicesgit clone --depth 1 https://github.com/shennawardana23/skillmeWrote 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/shennawardana23/skillme/best-practices)<a href="https://agentmods.dev/skills/shennawardana23/skillme/best-practices"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/best-practices/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/shennawardana23/skillme/best-practices"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/best-practices.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 | $0.00049 | $0.01644 |
| Opus 5 | $0.00024 | $0.00822 |
| Sonnet 5 | $0.00010 | $0.00329 |
| Haiku 4.5 | $0.00005 | $0.00164 |
Grade A, and why
best-practices 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 11d 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 — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Best practices
Modern web development standards based on Lighthouse best practices audits. Covers security, browser compatibility, and code quality patterns.
Security
HTTPS everywhere:
<!-- ❌ Mixed content -->
<img src="http://example.com/image.jpg">
<!-- ✅ HTTPS only -->
<img src="https://example.com/image.jpg">
Avoid protocol-relative URLs (//example.com/...) — they hide the actual scheme from reviewers. Send Strict-Transport-Security: max-age=31536000; includeSubDomains; preload.
Input sanitization:
// ❌ XSS vulnerable
element.innerHTML = userInput;
document.write(userInput);
// ✅ Safe text content
element.textContent = userInput;
// ✅ If HTML needed, sanitize
import DOMPurify from 'dompurify';
element.innerHTML = DOMPurify.sanitize(userInput);
Secure cookies (server-side):
Set-Cookie: session=abc123; Secure; HttpOnly; SameSite=Strict; Path=/
Beyond these, a real security posture needs: a CSP with nonces (script-src, frame-ancestors, base-uri, form-action); Trusted Types (require-trusted-types-for 'script') to stop raw strings reaching innerHTML/eval even under a strict CSP; Subresource Integrity hashes on every third-party <script>/<link> you don't control; the standard security-header set (HSTS, X-Content-Type-Options, Referrer-Policy, Permissions-Policy — never X-XSS-Protection, it's deprecated and was itself a vulnerability); and npm audit run regularly, watching specifically for prototype-pollution via recursive merges of untrusted input (_.merge, $.extend). Full syntax and code for all of these is in references/security-hardening.md — load it when implementing or auditing any of them.
Browser compatibility
Ship an HTML5 doctype, <meta charset="UTF-8"> as the first element in <head>, and a responsive viewport meta tag. Detect features ('IntersectionObserver' in window, CSS @supports), never sniff the user agent — UA strings are brittle and spoofable. Prefer bundling polyfills at build time (Babel/SWC + core-js) over runtime checks, and never load a polyfill from a third-party CDN you don't control — the 2024 polyfill.io supply-chain attack served malware to ~100k sites via exactly that pattern. Full markup and polyfill-loading code: references/compatibility-and-legacy-apis.md.
What ships with it
4 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.
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.
- 11d ago First seen · 120 lines · 49 tokens per session scan A 0e2a551e9f0b
best-practices is a skill published in the GitHub repository shennawardana23/skillme (2 stars, last pushed 13d ago), licensed Apache-2.0. It adds 49 tokens to every session and 1,644 once invoked, about $0.0002 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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