arktype-usage

A short set of rules for using Arktype, a TypeScript library for checking and describing data shapes. It applies when Arktype is needed instead of Zod, another data-validation library.

In plain words
What is it for?
It helps choose the correct Arktype syntax while writing or reviewing TypeScript code that validates data.
Why use it?
It prevents inconsistent Arktype patterns and common mistakes with optional fields, records, and arrays.

Cursor rule for Codex

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.

agentmods
npx agentmods add rules/prisma/orm/arktype-usage
Clone the repo
git clone --depth 1 https://github.com/prisma/orm

Made for: Codex.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 132 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00000 $0.00132
Opus 5 $0.00000 $0.00066
Sonnet 5 $0.00000 $0.00026
Haiku 4.5 $0.00000 $0.00013

Measured yesterday against content hash d1f83bba335a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

arktype-usage 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 yesterday.

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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

.agents/rules/arktype-usage.mdc · 17 lines

What it actually says

Arktype Usage Guidelines

This rulecard is intentionally short. For examples and edge cases, see docs/reference/arktype-usage.md.

Rules of thumb

  • Use optional keys via 'key?' (not string | undefined).
  • Use type({ '[string]': Schema }) for records.
  • Use Schema.array() for arrays (avoid tuple mistakes).
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. yesterday First seen · 17 lines · 0 tokens per session scan A d1f83bba335a

Subscribe to this mod's changes

arktype-usage is a cursor rule published in the GitHub repository prisma/orm (47,579 stars, last pushed today), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 132 tokens. 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.