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 agentmods add skills/nucliweb/webperf-snippets/webperfnpx skills add nucliweb/webperf-snippets --skill webperfgit clone --depth 1 https://github.com/nucliweb/webperf-snippetsWhat 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 | $0.00057 | $0.00471 |
| Opus 5 | $0.00028 | $0.00235 |
| Sonnet 5 | $0.00011 | $0.00094 |
| Haiku 4.5 | $0.00006 | $0.00047 |
Grade A, and why
webperf 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 2d 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
WebPerf Snippets Toolkit
A collection of 49 JavaScript snippets for measuring and debugging web performance in Chrome DevTools. Each snippet runs in the browser console and outputs structured, color-coded results.
Quick Reference
| Skill | Snippets | Trigger phrases |
|---|---|---|
| webperf-core-web-vitals | 7 | "debug LCP", "slow LCP", "CLS", "layout shifts", "INP", "interaction latency", "responsiveness" |
| webperf-loading | 29 | "TTFB", "slow server", "FCP", "render blocking", "font loading", "script loading", "resource hints", "service worker" |
| webperf-interaction | 9 | "jank", "scroll performance", "long tasks", "animation frames", "INP debug" |
| webperf-media | 3 | "image audit", "lazy loading", "image optimization", "video audit" |
| webperf-resources | 1 | "network quality", "bandwidth", "connection type", "save-data" |
Workflow
- Identify the relevant skill based on the user's question (see Quick Reference above)
- Load the skill's skill.md to see available snippets and thresholds
- Execute with Chrome DevTools MCP:
mcp__chrome-devtools__navigate_page→ navigate to target URLmcp__chrome-devtools__evaluate_script→ run the snippetmcp__chrome-devtools__get_console_message→ read results
- Interpret results using the thresholds defined in the skill
- Provide actionable recommendations based on findings
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.
- 2d ago First seen · 38 lines · 57 tokens per session scan A a4076330e9a2
webperf is a skill published in the GitHub repository nucliweb/webperf-snippets (1,445 stars, last pushed 1mo ago), licensed MIT. It adds 57 tokens to every session and 471 once invoked, about $0.0003 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 2026-08-30.
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