# Status codes and error messages (/en/api-reference/api-ref/conversational-ai/status-codes)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

Use HTTP status codes together with the `reason` and `detail` fields in error responses to troubleshoot failed Conversational AI REST API requests.

## HTTP status codes [#http-status-codes]

| Status code | Description                   | Suggested action                                                                                   |
| ----------- | ----------------------------- | -------------------------------------------------------------------------------------------------- |
| `200`       | OK                            | The request was successful.                                                                        |
| `400`       | Invalid request parameters    | Check the `detail` field for specific information.                                                 |
| `401`       | Authentication failed         | Check the `Authorization` header, credentials, or token and retry.                                 |
| `403`       | Unauthorized access           | Resolve account or billing issues, or contact technical support to activate the service.           |
| `404`       | Agent not found or has exited | Check whether the agent started successfully or has already stopped.                               |
| `409`       | Agent conflict                | Use the task information returned by the server to continue, or retry with a different agent name. |
| `422`       | Access limit exceeded         | Contact technical support to raise your quota.                                                     |
| `429`       | Request rate limit exceeded   | Retry using a backoff strategy.                                                                    |
| `500`       | Internal server error         | If the problem persists, contact technical support.                                                |
| `502`       | Gateway error                 | Contact technical support.                                                                         |
| `503`       | Agent startup failure         | Retry using a backoff strategy.                                                                    |
| `504`       | Request timeout               | Retry using a backoff strategy.                                                                    |

## Error reasons [#error-reasons]

| Reason                       | Description                                                                               |
| ---------------------------- | ----------------------------------------------------------------------------------------- |
| `ServiceNotEnabled`          | The service is not enabled for the current project.                                       |
| `AccountSuspended`           | The account has been suspended and the service is unavailable.                            |
| `InternalError`              | Internal error on the server.                                                             |
| `InvalidPermission`          | The service is not activated.                                                             |
| `InvalidRequestBody`         | The request body is not valid JSON.                                                       |
| `MissingRequiredField`       | A required field is missing from the request.                                             |
| `InvalidFieldValue`          | A request field contains an invalid value.                                                |
| `ResourceQuotaLimitExceeded` | Too many concurrent requests, exceeding the quota limit.                                  |
| `ConcurrencyLimitExceeded`   | Too many concurrent requests, exceeding the quota limit.                                  |
| `ServiceUnavailable`         | The service is temporarily unavailable.                                                   |
| `ResourceAllocationFailed`   | The required resources cannot be allocated at this time.                                  |
| `TaskConflict`               | An agent with the same name already exists, or a conflicting task is already running.     |
| `TaskNotFound`               | The task was not started successfully, was aborted after starting, or has been destroyed. |
| `TaskOperationTimeout`       | Internal error on the server.                                                             |
| `NotImplemented`             | Internal error on the server.                                                             |