Schemas

t.string().min(1).max(60).email().uuid().pattern(/x/).format("date-time").trim()
t.int().min(0)   t.number().positive()   t.boolean()
t.enum(["a", "b"])   t.literal("a")   t.union(t.string(), t.int())
t.array(Tea).min(1)   t.record(t.int())   t.any()   t.empty()   t.problem()
t.object({ … }).strict() .passthrough() .pick() .omit() .extend() .partial()

.optional()  .nullable()  .default(v)  .describe("…")  .example(v)  .named("Tea")  .deprecated()

Infer<typeof Tea> is the TypeScript type. Tea.parse(x) throws a ValidationError, Tea.safeParse(x) does not, and Tea.toJSONSchema() gives JSON Schema 2020-12.

t.date() accepts ISO date-time strings (including a timezone) or valid Date instances and returns a Date. Responses serialize dates back to ISO strings; the wire schema is { type: "string", format: "date-time" }.

const Even = t.int().refine(n => n % 2 === 0, "must be even");
const Length = t.string().transform(text => text.length); // Infer: number
const Pet = t.discriminated("kind", {
  cat: t.object({ kind: t.literal("cat"), lives: t.int() }).named("Cat"),
  dog: t.object({ kind: t.literal("dog"), bark: t.boolean() }).named("Dog"),
});

type Node = { name: string; children: Node[] };
const Node: Schema<Node> = t.object({
  name: t.string(), children: t.array(t.lazy(() => Node)),
}).named("Node"); // import type { Schema } from "@vxnsin/inkan"

Refinements and transforms are synchronous, run in chain order after successful validation, and remain outside JSON Schema. Transforms document their original input shape; use them on request schemas when the parsed handler value differs from the wire value. Optional, nullable and default modifiers added after an effect bypass that effect for their missing/null/default values. Modifiers before an effect supply its input.

Each discriminated branch declares its matching literal tag. OpenAPI uses oneOf and a discriminator, with mappings for named branches. Name recursive shapes so OpenAPI can reference components; toJSONSchema() includes named schemas in $defs, making its references self-contained.