Add one or more contacts to an existing list
added count reflects only newly added contacts.| Status | Code | Description |
|---|---|---|
| 400 | validation_error | Invalid contact IDs or exceeds 100 limit |
| 401 | invalid_key | Invalid API key |
| 403 | insufficient_permissions | Missing write permission |
| 404 | not_found | List not found or not in your workspace |
| 429 | rate_limited | Rate limit exceeded |