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 kid-sid/codex-spellbook --skill typescriptgit clone --depth 1 https://github.com/kid-sid/codex-spellbookWrote 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/kid-sid/codex-spellbook/typescript)<a href="https://agentmods.dev/skills/kid-sid/codex-spellbook/typescript"><img src="https://agentmods.dev/badge/skills/kid-sid/codex-spellbook/typescript/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/kid-sid/codex-spellbook/typescript"><img src="https://agentmods.dev/badge/skills/kid-sid/codex-spellbook/typescript.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 | $0.00047 | $0.00649 |
| Opus 5 | $0.00023 | $0.00324 |
| Sonnet 5 | $0.00009 | $0.00130 |
| Haiku 4.5 | $0.00005 | $0.00065 |
Grade A, and why
typescript 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 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.
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.
How it starts
The opening of the file, as written. The whole thing — 101 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TypeScript
Use the type system aggressively at compile time and Zod at runtime so invalid states are hard to represent and easy to reject.
When to Activate
- Configure a new TypeScript service
- Add request parsing or input validation
- Replace
anyin an existing module - Model variant-heavy state or workflow results
- Choose ESM or CJS for a package
- Introduce path aliases in a growing codebase
- Write or review Vitest suites
Compiler and Validation
| Setting | Expectation |
|---|---|
strict |
true |
noUncheckedIndexedAccess |
enabled |
exactOptionalPropertyTypes |
enabled when practical |
moduleResolution |
aligned to runtime and bundler |
BAD
const body = req.body as CreateUserInput;
GOOD
const CreateUserSchema = z.object({
email: z.string().email(),
name: z.string().min(1),
});
const body = CreateUserSchema.parse(req.body);
Type Modeling
| Problem | Preferred | Avoid |
|---|---|---|
| Heterogeneous state | Discriminated union | Optional field soup |
| External JSON | unknown then parse |
any |
| Recoverable failure | Result<T, E> style return |
Throwing for normal control flow |
BAD
type Payment = {
status?: "pending" | "paid";
error?: string;
receiptUrl?: string;
};
GOOD
type Payment =
| { status: "pending" }
| { status: "paid"; receiptUrl: string }
| { status: "failed"; error: string };
Modules and Testing
| Situation | Choice |
|---|---|
| New Node 20+ service | ESM |
| Legacy toolchain locked to CJS | CJS until migration is funded |
| Mixed environment | Hide format behind build output boundary |
| Preferred | Avoid |
|---|---|
Stable aliases like @/domain/user |
Deep relative imports like ../../../../user |
| Match runtime and TS config | Compile-only aliases that break at runtime |
| Rule | Why |
|---|---|
| Co-locate or mirror test files consistently | Easier navigation |
Use vi.mock only at unstable boundaries |
Preserve real type interactions |
| Keep fake timers explicit | Avoid hidden temporal coupling |
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 · 101 lines · 47 tokens per session scan A a3075f9be1bc
typescript is a skill published in the GitHub repository kid-sid/codex-spellbook (21 stars, last pushed 4mo ago), licensed MIT. It adds 47 tokens to every session and 649 once invoked, about $0.0002 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 2026-09-03.
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