# Errors

> Four Echelon APIs return structured errors with a message and type. Treat non-2xx responses as failed requests and preserve request ids for debugging and support.

Source: https://fourechelon.com/docs/errors · Machine-readable: https://fourechelon.com/openapi.json · Index: https://fourechelon.com/llms.txt

## Error types

| Status | Type | Meaning |
| --- | --- | --- |
| 400 | invalid_request_error | Malformed JSON or unsupported model id. |
| 401 | authentication_error | Missing, revoked, or invalid API key. |
| 402 | payment_required | An active or trialing paid API subscription is required. |
| 413 | request_too_large | Request body exceeds the configured byte limit. |
| 415 | unsupported_file_type | SolidWorks native and other unsupported CAD formats. Export STEP and retry. |
| 422 | schema_error | Spatial input does not satisfy the expected schema. |
| 429 | rate_limit_error | Per-key rate limit exceeded. Retry after a short delay. |
| 503 | runtime_error | Hosted runtime is unreachable and no fallback can complete the request. |