| 200 | OK | Successful request | — |
| 400 | Bad Request | Invalid JSON, missing/invalid fields (user, type), unsupported type | Fix the request and retry |
| 401 | Unauthorized | Missing/invalid Bearer token or API key | Add valid Authorization: Bearer <token> |
| 403 | Forbidden | Authenticated but not allowed for this resource/plan | Upgrade plan or contact support |
| 404 | Not Found | Wrong path/route | Check the endpoint path |
| 429 | Too Many Requests | Per-token or per-token+IP rate limit exceeded | Honor Retry-After; backoff + jitter |
| 500 | Internal Server Error | Unexpected server error | Retry with exponential backoff |
| 502 | Bad Gateway | Upstream providers failed; no fresh/stale data available | Retry/backoff; try the other region (EU/JP) |
| 503 | Service Unavailable | Maintenance window or temporary overload | Retry after a short delay |
