# SDKError.cause

```ts
cause?: unknown
```

What was caught, when this wraps another error — the standard `Error.cause`, kept for a host's logs. `activateTool()` rejects with `UNKNOWN_ERROR` carrying the cause of a tool that could not start.

- Kind: property
- Since: 1.0.0

Returns `unknown`

Part of [SDKError](https://kernstra.com/docs/web-sdk/api/sdkerror) in the Kernstra Web SDK 1.0.0 API reference.

Web page: https://kernstra.com/docs/web-sdk/api/sdkerror/cause