> For the complete documentation index, see [llms.txt](https://rjdellecese.gitbook.io/confect/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://rjdellecese.gitbook.io/confect/schema-restrictions.md).

# Schema restrictions

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

```typescript
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 provided as an argument/returned as a value in 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.

{% code title="✅" %}

```typescript
export const myQuery = query({
  args: Schema.Struct({}),
  returns: Schema.Null,
  handler: () => Effect.succeed(null),
})
```

{% endcode %}

{% code title="❌" %}

```typescript
export const myQuery = query({
  args: Schema.Struct({}),
  returns: Schema.Undefined,
  handler: () => Effect.succeed(undefined),
})
```

{% endcode %}

{% code title="❌" %}

```typescript
export const myQuery = query({
  args: Schema.Struct({}),
  returns: Schema.Void,
  handler: () => Effect.void,
})
```

{% endcode %}