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

# MCP Error Handling

> Handling MCP communication and proxied Byul API errors

## Common error format

Errors proxied from REST follow the same format as in the REST docs:

```json theme={null}
{
  "statusCode": 401,
  "message": "API key is required. Please provide a valid V2 API key in the X-API-Key header.",
  "error": "Unauthorized",
  "timestamp": "2024-01-15T10:30:00.123Z",
  "path": "/api/v2/news"
}
```

## Frequent issues

* `Missing BYUL_API_KEY environment variable` → set the environment variable before launching
* `Rate limit exceeded` → apply backoff/retry per REST guidance

## Retry guidance

<Tip>
  Apply exponential backoff for 429 and 5xx responses. You can reuse the REST examples as-is.
</Tip>