# event-schema-not-object

A **[schema](/learn/tutorials/first-steps-with-eventsourcingdb/registering-event-schemas)** does **not describe an object** at its top level.

- **Routes:** `register-event-schema` and `restore-backup`
- **Description:** `event schema does not describe an object: expected type 'object', since the data of an event is always a JSON object`
- **Details:** When registering a schema, none; `details` is an empty object. When restoring a backup, **`part`**, the part of the backup that holds the schema, counting from 0, with the full backup as part 0, and **`value`**, the event type of the schema.

## Why It Happens

The **[data of an event](/docs/eventsourcingdb/cloud-events)** is always a JSON object, so a schema for it has to say so with **`"type": "object"`** at its top level. A schema that leaves out `type`, such as `{}`, that names another type, such as `"string"`, or that only refers to a definition with `$ref` at its top level is refused. The top-level `type` has to be **exactly the string `"object"`**, so a list such as `["object"]` is refused as well. JSON Schema knows the keyword as **`type`** alone, so a member that spells it otherwise, such as `Type` or `TYPE`, says nothing about the type: `{"TYPE": "object"}` is refused as a schema that names no type, and so is `{"type": "string", "TYPE": "object"}`, which describes a string.

A schema that is not a valid JSON Schema at all is reported as **[`event-schema-malformed`](/docs/eventsourcingdb/errors/event-schema-malformed)** instead, since that is checked first. When restoring a backup, every schema of the backup is checked the same way, as it is read, also in a backup that the v1 API created. Restoring such a backup through the v1 API refuses the schema as well, with a `400`, see **[Compatibility](/docs/eventsourcingdb/backup-and-restore#compatibility)**.

## How to Fix It

Put `"type": "object"` at the top level of the schema, also next to a `$ref` that refers to a definition of the object. Sending the same request again fails the same way, since the error depends on the schema alone.

## Example

To register a schema for `io.eventsourcingdb.library.book-acquired` that only refers to the definition `#/$defs/book` with `$ref` at its top level, EventSourcingDB answers with this error, as a line of the stream, and then ends the stream with its `end` item:

```json
{
  "type": "error",
  "data": {
    "code": "https://docs.eventsourcingdb.io/errors/event-schema-not-object",
    "description": "event schema does not describe an object: expected type 'object', since the data of an event is always a JSON object",
    "details": {}
  }
}
```