## API Request to Update User Segments

### Request Parameters
- **networkId**: `int32` (required)  
  Your account (network) ID  
- **userKey**: `string` (required)  
  The user ID to update  
- **group**: `integer` (optional)  
  Sets the user's incrementality group (1–100) as part of this request; use `group=null` to clear it, or omit to leave it unchanged. Invalid values reject the entire request.  
- **segments**: `array of int32s` (required)  
  The segments to add.

### Header Parameters
- **accept**: `string`  
  Defaults to application/json.  
  Allowed: `application/json`, `text/plain`

### Response Codes
- **200**: Successful update, returns the updated segments.
- **400**: Bad request, invalid parameters.

### Example API Call

```bash
curl --request PUT \
     --url https://e-networkId.adzerk.net/udb/networkId/segments \
     --header 'accept: application/json' \
     --header 'content-type: application/json'
```

### Example Request Body
```json
{
  "key": "ue1-e397eb5990",
  "segments": [
    40,
    41,
    42
  ]
}
```