# AI Agent API Error Catalog

This section documents the errors that AI Agent APIs may return (standard error messages are described in [Common API Error Catalog](/celonis-apis/api-reference/common-error-catalog)).

| **Returned when**   | **Response**  |
|  --- | --- |
|  | **Status code** | **Example** |
| Referencing a non-existing Celonis Process Copilot. | 400 | 
```javascript
  { 
     "title": "AI Agent not found.",
      "status": 400,
      "detail": "AI Agent with id 'XXXX' was not found.",
      "errorCode": "AGENT_NOTFOUND"
   }
```
 |
| Either the specified agent is unavailable or your account doesn't have permission to use it. | 400 | 
```javascript
  { 
      "title": "Access denied.",
      "status": 400,
      "detail": "Agent access denied.",
   }
```
 |
| Referencing an agent you don't have access to | 403 | 
```javascript
  { 
      "title": "Access denied.",
      "status": 403,
      "detail": "Agent access denied.",
   }
```
 |
| Access to the Chat conversation endpoint is forbidden because the feature has not been enabled for the requested Asset. This usually means the External Integrations UI Toggle is currently disabled.**Remediation:** Follow the enablement steps in Getting Started. | 403 | 
```javascript
  { 
      "title": "Chat API is not enabled for external use.",
      "status": 403,
      "detail": "Chat API is not enabled for this Process Copilot. Enable it in the Process Copilot's integrations configuration.",
   }
```
 |