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/xobotyi/cc-foundry/javascriptnpx skills add xobotyi/cc-foundry --skill javascriptgit clone --depth 1 https://github.com/xobotyi/cc-foundryWhat 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 | $0.00047 | $0.03930 |
| Opus 5 | $0.00023 | $0.01965 |
| Sonnet 5 | $0.00009 | $0.00786 |
| Haiku 4.5 | $0.00005 | $0.00393 |
Grade B, and why
javascript scanned grade B 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 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.
Strips warnings and disclaimersmediumAnti-refusal
Omitting safety caveats hides risk from the user and is a common jailbreak preamble.
- Don't lecture or quote the rule — state what's wrong and how to fix it. How it starts
The opening of the file, as written. The whole thing — 280 lines — stays where its author put it; the contents beside it link to each section on GitHub.
JavaScript
Clarity is the highest JavaScript virtue. If your code requires a comment to explain its control flow, rewrite it.
JavaScript rewards explicit, readable code. Prefer boring patterns that are easy to understand over clever tricks that save characters.
References
- Functions, closures, composition → [
${CLAUDE_SKILL_DIR}/references/functions.md] — Arrow function examples, closure patterns, early return, parameter destructuring - Async patterns, error handling, concurrency → [
${CLAUDE_SKILL_DIR}/references/async.md] — Promise.all/race/any examples, cancellation, custom error classes, for-await - Objects, arrays, iteration, Map/Set → [
${CLAUDE_SKILL_DIR}/references/objects-and-arrays.md] — Iteration decision table, destructuring patterns, immutable updates, generators - ES modules, imports, barrel files → [
${CLAUDE_SKILL_DIR}/references/modules.md] — Import ordering, barrel file rationale, directory import pitfalls, dynamic imports - JSDoc typing, full tag catalog → [
${CLAUDE_SKILL_DIR}/references/jsdoc.md] — Full tag reference (@callback, @template, @enum), type assertions, class modifiers - General JS idioms and edge cases → [
${CLAUDE_SKILL_DIR}/references/idioms.md] — Variable/naming examples, equality coercion table, modern syntax patterns
Variables and Declarations
constby default. Useletonly when reassignment is required. Nevervar.constprevents reassignment, not mutation. Objects and arrays declared withconstcan still be mutated.- Block scope only.
let/constare block-scoped;varis function-scoped and hoists — this causes bugs in loops and conditionals. - One declaration per line. Never chain
const a = 1, b = 2. - Group declarations.
constfirst, thenlet.
Naming
| Entity | Style | Examples |
|---|---|---|
| Variables, functions | camelCase | userName, fetchData |
| Classes, constructors | PascalCase | UserService, HttpClient |
| True compile-time constants | SCREAMING_SNAKE_CASE | MAX_RETRIES, API_BASE_URL |
| Private fields/methods | # prefix (class) |
#count, #validate() |
| Booleans | is/has/can/should prefix |
isValid, hasAccess |
| File names | kebab-case or camelCase | user-service.js, userService.js |
What ships with it
7 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.
- 2d ago First seen · 280 lines · 47 tokens per session scan B a72f075621f1
javascript is a skill published in the GitHub repository xobotyi/cc-foundry (20 stars, last pushed 2d ago), licensed MIT. It adds 47 tokens to every session and 3,930 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it B with 1 finding (strips warnings and disclaimers). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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