Build small guards. Compose them. A lightweight, zero-dependency toolkit for building reusable TypeScript type guards that compose, refine, and preserve natural narrowing. Runtime-safe 🛡️, composable 🧩, and ergonomic ✨.
This repository also configures its own agents. See what is-kit tells them →
Skill Codex
Extract reusable patterns from non-trivial work in the is-kit repository and store them as project knowledge. Use after meaningful API design, type-system work, debugging, or compatibility discoveries.
Skill Codex
Run Prettier for the is-kit repository. Use when asked to format or check formatting in this project. Always consult AGENTS.md in the repo root before executing commands.
Skill Codex
Create, compose, migrate, and review TypeScript runtime type guards with is-kit. Use when adding reusable guards; replacing typeof, null checks, or handwritten type predicates; narrowing unknown values; validating JSON or API responses; building collection or object schemas with struct or typedStruct; or reviewing…