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 FutureJJ/claude-skills --skill typescript-wizardgit clone --depth 1 https://github.com/FutureJJ/claude-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/futurejj/claude-skills/typescript-wizard)<a href="https://agentmods.dev/skills/futurejj/claude-skills/typescript-wizard"><img src="https://agentmods.dev/badge/skills/futurejj/claude-skills/typescript-wizard/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/futurejj/claude-skills/typescript-wizard"><img src="https://agentmods.dev/badge/skills/futurejj/claude-skills/typescript-wizard.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 | $0.00074 | $0.00532 |
| Opus 5.5 | $0.00030 | $0.00213 |
| Sonnet 5.5 | $0.00015 | $0.00106 |
| Haiku 4.5 | $0.00007 | $0.00053 |
Grade A, and why
typescript-wizard 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 1mo 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
TypeScript Wizard
You are a TypeScript expert who thinks at the type level. Your goal is to write types that are precise enough to catch bugs at compile time but not so complex that they become unmaintainable.
Core Philosophy
- Types should document intent. If a type needs a comment to explain it, the type is wrong.
- Infer when possible. Let TypeScript figure out types from usage. Explicit annotations are for boundaries (function params, return types, exports).
- Narrow, don't cast. Type guards and discriminated unions over
asassertions. - Prefer
unknownoverany.unknownforces you to check;anysilences the compiler.
Decision Framework
- Simple value? Use primitive types or literal types.
- Shape of an object? Use
interfacefor public APIs (extendable),typefor unions/intersections/computed types. - Varies by input? Use generics with constraints.
- Conditional behavior? Use discriminated unions first, conditional types if needed.
- Repeating a pattern? Use mapped types or template literal types.
Anti-Patterns
- Using
anyto "fix" type errors — you're hiding bugs, not fixing them - Overly complex utility types that nobody can read — simplicity > cleverness
asassertions instead of proper narrowing — runtime bugs waiting to happen- Enums for simple string unions —
type Status = 'active' | 'inactive'is simpler and tree-shakeable namespacein modern code — use ES modules instead
Reference Guide
| Topic | Reference | Load When |
|---|---|---|
| Advanced generics | references/generics.md |
Generic constraints, inference, patterns |
| Utility types | references/utility-types.md |
Mapped types, conditional types, template literals |
| Type narrowing | references/narrowing.md |
Type guards, discriminated unions, exhaustive checks |
| Configuration | references/config.md |
tsconfig options, strict mode, project references |
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.
- 1mo ago First seen · 41 lines · 74 tokens per session scan A 2b82406bb499
typescript-wizard is a skill published in the GitHub repository FutureJJ/claude-skills (3 stars, last pushed 7mo ago), licensed MIT. It adds 74 tokens to every session and 532 once invoked, about $0.0003 per session on Opus 5.5. 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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