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

# Error Handling

GraphQL operations return errors in a standardized format:

* Each response may include an `errors` array
* Each error contains:
  * `message`: Human-readable error description
  * `extensions`: Additional metadata and error codes

Always check the error object in the response rather than HTTP status codes. Examples below demonstrate common error scenarios.

## Example 1: GraphQL Validation Error

```json theme={null}
{
  "errors": [
    {
      "message": "Cannot query field \"UID\" on type \"Device\". Did you mean \"UUID\" or \"_id\"?",
      "locations": [
        {
          "line": 5,
          "column": 5
        }
      ],
      "extensions": {
        "code": "GRAPHQL_VALIDATION_FAILED"
      }
    }
  ]
}
```

## Example 2: Device Already Paired Error

```json theme={null}
{
  "errors": [
    {
      "message": "This device is already paired",
      "extensions": {
        "code": "406",
        "response": {
          "statusCode": 406,
          "message": "This device is already paired",
          "error": "Not Acceptable"
        }
      }
    }
  ],
  "data": null
}
```

### Explanation

* **GraphQL Validation Error**: This example shows an error when a field is queried incorrectly. It includes a message, location, and an error code.
* **Device Already Paired Error**: This example shows a business logic error with a specific status code and message.