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 existing is-kit usage. Do not use for one-off environment checks or validation that requires data transformation or rich error reporting.
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.
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.
