| 202 | Accepted — an async operation was accepted and completes in the background (campaign delete/archive). Not an error. |
| 400 | Bad request — malformed input or failed request validation. |
| 401 | Unauthorized — missing or invalid API key. |
| 403 | Forbidden — insufficient permissions for the resource or action. |
| 404 | Not found — resource does not exist or is not visible to this key. |
| 409 | Conflict — the action can’t proceed in the current state (e.g. the sending LinkedIn account is disconnected). |
| 422 | Unprocessable entity — semantic validation failed (e.g. messaging a lead that has no existing conversation). |
| 429 | Too many requests — endpoint rate limit, or the per-account messaging send budget, exceeded; see Rate limiting. |
| 500 | Unexpected server error — retry with backoff; contact support if it persists. |
| 502 | Bad gateway — an upstream provider (LinkedIn via Unipile) failed on a send; retry with backoff. |
| 503 | Service unavailable — a required dependency isn’t configured or available (e.g. messaging is not configured). |