language

language is a skill for Claude Code from vinnie357/claude-skills. It costs 51 tokens per session (2,795 once invoked), scanned A, original, MIT.

A guide to TypeScript’s type system and core language features, including strict checking, utility types, generics, declaration files, and discriminated unions.

In plain words
What is it for?
Writing or reviewing TypeScript types, configuring strict mode, designing generics, choosing utility types, and creating declaration files.
Why use it?
It helps catch unclear values, missing null checks, and other type-related mistakes before they become runtime bugs. It also provides guidance for modeling data consistently.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the typescript plugin — 3 skills shipped together

Good fit Writing or reviewing TypeScript types, configuring strict mode, designing generics, choosing utility types, and creating declaration files.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/vinnie357/claude-skills/language
Install

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.

Any agent
npx skills add vinnie357/claude-skills --skill language
Clone the repo
git clone --depth 1 https://github.com/vinnie357/claude-skills

Made for: Claude Code.

Or install typescript, the plugin that ships this one along with the rest of its 3 skills.

Wrote 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.

agentmods badge for language

README.md
[![agentmods](https://agentmods.dev/badge/skills/vinnie357/claude-skills/language/github.svg)](https://agentmods.dev/skills/vinnie357/claude-skills/language)
Your own site
<a href="https://agentmods.dev/skills/vinnie357/claude-skills/language"><img src="https://agentmods.dev/badge/skills/vinnie357/claude-skills/language/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.

agentmods 80×15 button for language

Your own site · 80×15
<a href="https://agentmods.dev/skills/vinnie357/claude-skills/language"><img src="https://agentmods.dev/badge/skills/vinnie357/claude-skills/language.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,795 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Memory Poisoning · line 32
    Skill manipulates agent memory, state, or stored context. Memory corruption can alter personality, override safety rules, or cause unpredictable behavior.
    Fix: Protect agent memory and state from modification by untrusted content. Use read-only memory for critical instructions and validate all state changes.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00051 $0.02795
Opus 5 $0.00026 $0.01398
Sonnet 5 $0.00010 $0.00559
Haiku 4.5 $0.00005 $0.00280

Measured 9d ago against content hash 46a93ebcfb94, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

language 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 9d 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.

plugins/languages/typescript/skills/language/SKILL.md · 227 lines

How it starts

The opening of the file, as written. The whole thing — 227 lines — stays where its author put it; the contents beside it link to each section on GitHub.

TypeScript Language

Core TypeScript: strict mode, the type system, utility types, declaration files, and discriminated unions.

Strict Mode

strict: true in tsconfig.json is the floor for new TypeScript code in this workspace, not an opt-in extra. It is a single flag that enables a family of component flags — turn it on first, then reach for a component flag only when you need something strict doesn't cover.

{
  "compilerOptions": {
    "strict": true
  }
}

strict enables, among others:

Flag What it catches
noImplicitAny A variable or parameter would be inferred as any because no annotation is present
strictNullChecks null/undefined stop being implicitly assignable to every type
strictFunctionTypes Function parameter types are checked contravariantly instead of bivariantly
strictBindCallApply .call/.bind/.apply are checked against the underlying function's signature
strictPropertyInitialization A class field must be assigned in the constructor or have a definite-assignment marker
noImplicitThis this inside a function with unclear context is flagged instead of defaulting to any
alwaysStrict Every emitted file is parsed as, and emits, ECMAScript strict mode
useUnknownInCatchVariables catch (e) types e as unknown, not any — forces a type check before use

Two flags strict does not enable — they are separate opt-ins the strict family does not imply, though a current tsc --init now writes both into a fresh project's generated tsconfig.json alongside strict: true (listed under its own "Stricter Typechecking Options" heading, not inside the strict block itself):

  • exactOptionalPropertyTypes — an optional property (foo?: string) rejects an explicit undefined assignment unless the type says foo?: string | undefined. Catches call sites that "clear" a field by writing undefined when the schema meant "omit it."
  • noUncheckedIndexedAccess — indexing into a Record<string, T> or array by a computed key returns T | undefined instead of T, since JavaScript doesn't guarantee the key exists.

Read the full file on GitHub · 227 lines

Files

What ships with it

1 file 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.

Changes

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.

  1. 9d ago First seen · 227 lines · 51 tokens per session scan A 46a93ebcfb94

Subscribe to this mod's changes

language is a skill published in the GitHub repository vinnie357/claude-skills (25 stars, last pushed 2d ago), licensed MIT. It adds 51 tokens to every session and 2,795 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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