> ## Documentation Index
> Fetch the complete documentation index at: https://confect.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Schema Restrictions

> Understand the restrictions on Effect schemas that can be used in Confect.

Not every Effect `Schema` is valid for use in Confect. Remember that an Effect `Schema` looks like this:

```typescript theme={null}
type Schema<Type, Encoded, Context>
```

For `Schema`s used in Confect:

* `Type` represents the value that you'll be operating on in your code. Any TypeScript type is permitted here.
* `Encoded` represents the value that is stored in the database or serialized as the argument/output of a Convex function. This must be a valid [Convex value](https://docs.convex.dev/database/types#convex-values).
* `Context` is not currently supported. It should always be `never`.

## Additional caveats

### No-op returns from Convex functions

Unlike the vanilla APIs, Convex functions defined with Confect may not return `undefined` or `void`—use `null` (`Schema.Null` as the `returns` validator) instead. Convex coerces `undefined`/`void` returns to `null` anyways—this just makes that more explicit.

```typescript ✅ theme={null}
FunctionSpec.publicQuery({
  name: "myQuery",
  args: () => Schema.Struct({}),
  returns: () => Schema.Null,
});
```

```typescript ❌ theme={null}
FunctionSpec.publicQuery({
  name: "myQuery",
  args: () => Schema.Struct({}),
  returns: () => Schema.Undefined,
});
```

```typescript ❌ theme={null}
FunctionSpec.publicQuery({
  name: "myQuery",
  args: () => Schema.Struct({}),
  returns: () => Schema.Void,
});
```