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 jscraik/Agent-Skills --skill javascript-progit clone --depth 1 https://github.com/jscraik/Agent-SkillsWrote 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/jscraik/agent-skills/javascript-pro)<a href="https://agentmods.dev/skills/jscraik/agent-skills/javascript-pro"><img src="https://agentmods.dev/badge/skills/jscraik/agent-skills/javascript-pro.svg" alt="Measured on agentmods" 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 | $0.00037 | $0.00643 |
| Opus 5 | $0.00018 | $0.00321 |
| Sonnet 5 | $0.00007 | $0.00129 |
| Haiku 4.5 | $0.00004 | $0.00064 |
Grade A, and why
javascript-pro scanned grade A with 1 finding 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 5d 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
const response = await fetch(url) How it starts
The opening of the file, as written. The whole thing — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Table of Contents
When to use
- Use for JavaScript implementation and review tasks.
- Use when async behavior or runtime compatibility is critical.
Required inputs
- Target runtime and module format.
- Files or functions to update.
- Error or performance constraints.
Deliverables
- Behavior-correct JavaScript changes.
- Clear async flow and explicit error handling.
- Compatibility notes when needed.
Core Practices
- Prefer small pure functions for transformation logic.
- Use
constby default,letonly when reassignment is required. - Keep API surfaces explicit and documented through JSDoc when needed.
Async Safety
-
Await every promise that affects correctness.
-
Use
Promise.allonly for truly independent operations. -
Surface actionable errors with context.
-
Redact secrets, tokens, credentials, and sensitive data by default.
Examples
export async function loadJson(url) {
const response = await fetch(url)
if (!response.ok) throw new Error(`Fetch failed: ${response.status}`)
return response.json()
}
Failure mode
- If side effects cannot be isolated, keep behavior unchanged and document risk.
Gotchas
- Unawaited promises can mask production failures.
See Also
| Skill | When to use |
|---|---|
| [[typescript]] | Typed JavaScript superset when strict contracts and module boundaries are needed |
| [[biome-linting]] | Enforce JavaScript/TypeScript lint and format rules with Biome |
Topic map: [[agent-ops]]
Philosophy
- Optimize for clear, verifiable outcomes with the minimum necessary changes.
- Keep guidance deterministic so repeated runs produce consistent decisions.
Procedure
- Confirm scope, constraints, and required inputs before edits.
- Apply focused changes tied directly to the requested outcome.
- Re-run the highest-signal validations and capture concrete evidence.
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.
- 5d ago First seen · 105 lines · 37 tokens per session scan A 875bba0a46ee
javascript-pro is a skill published in the GitHub repository jscraik/Agent-Skills (8 stars, last pushed 7d ago), licensed Apache-2.0. It adds 37 tokens to every session and 643 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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