Schema Libraries

Synced-store uses any Standard Schema-compliant library (Zod, Valibot, ArkType) or plain JSON Schema. Schemas are used for compile-time type inference only — no runtime validation.

Zod is the default in most examples. When you need to avoid Zod's bundle size or prefer a different style, use one of these.

Valibot

import * as v from "valibot";
import { defineSchema, table } from "poe-apps-sdk/v1/backend.js";

const schema = defineSchema({
  schemaVersion: 1,
  tables: {
    todos: { schema: table(v.object({ text: v.string(), done: v.boolean() })) },
  },
  mutators: {
    setTodo: { description: "...", input: v.object({ id: v.string(), text: v.string() }) },
  },
});

JSON Schema (no library needed)

Useful when you don't want to pull in a validation library, or when the schema is already expressed as JSON Schema elsewhere.

import { jsonSchema } from "poe-apps-sdk/v1/backend.js";
import { defineSchema, table } from "poe-apps-sdk/v1/backend.js";

const schema = defineSchema({
  schemaVersion: 1,
  tables: {
    todos: {
      schema: table(jsonSchema<{ text: string; done: boolean }>({
        type: "object",
        properties: {
          text: { type: "string" },
          done: { type: "boolean" },
        },
        required: ["text", "done"],
      })),
    },
  },
});

The TypeScript generic on jsonSchema<T>() is the source of truth for types. The JSON Schema object itself is carried through for tooling (e.g. MCP tool definitions).

When to pick which

• Zod — the default; richest ecosystem and best error messages. Costs ~280KB gzipped on the client if bundled — use type-only imports in client-config.ts to avoid this.
• Valibot — tree-shakable, much smaller bundle; same mental model as Zod.
• JSON Schema — zero runtime dependency; use when you want the schema to be consumed by external tools (or when the schema is hand-written elsewhere).