---
title: "authentication_failed"
description: "Error cause: authentication_failed"
canonical: "https://studio.inttegro.dev/e/c-authentication_failed"
format: inttegro-machine-docs/v1
language: "C#"
sdk_version: "v13.1.0"
reader_profile: optional
reader_manifest: "https://studio.inttegro.dev/machine/csharp/readers/index.json"
reader_identification: "Optional: declare your client only if known and your current-session capabilities; use reader_manifest for supplemental recommendations."
preamble_estimated_tokens: 356
model_token_report: "https://studio.inttegro.dev/machine/token-report.json"
preamble_questions: 5
preamble_source: "general"
recommended_mcp_tools: []
estimated_tokens: 998
token_estimate_method: "utf8_bytes_divided_by_4"
---

## Machine preamble

**Summary:** Error cause: authentication_failed This C# representation uses the selected SDK's native names wherever Studio has a verified mapping.

### Five questions

#### Q1. When should the reader use authentication_failed?

Use this page as orientation before selecting the narrower guide or reference that owns the implementation contract.

#### Q2. What is authoritative on this page?

Use this page for orientation; follow its canonical SDK, guide, API, or MCP links for exact contracts.

#### Q3. What page-specific constraint matters most?

Use the page to choose a canonical next source instead of treating summary material as a complete implementation contract.

#### Q4. Can Inttegro MCP materially help with this task?

No catalog ability is sufficiently specific to recommend for this page. Use the documentation directly; consult the MCP catalog only if the task later requires governed live account context or a supported operation.

#### Q5. How should the reader verify the answer and continue?

Select the narrowest linked guide or reference, apply its stated completion condition, and verify against authoritative resource state when the task changes data. Continue with [bad_request](https://studio.inttegro.dev/machine/csharp/e/t-bad_request.md) and [authorization_failed](https://studio.inttegro.dev/machine/csharp/e/c-authorization_failed.md) when those concerns enter scope.

## Document content

# authentication\_failed

Error cause indicating authentication failed due to missing, invalid, or expired credentials.

## What this means

The Inttegro API could not verify your identity because the API key or authentication token provided in your request is missing, malformed, invalid, or has expired. Every API request must include a valid API key in the `Authorization` header using the format `Authorization: Bearer $INTTEGRO_API_KEY`. When this cause appears, it means the authentication layer rejected your credentials before the request even reached the business logic—for example, creating a new order without an `Authorization` header, or using a revoked API key.

This differs from `authorization_failed` where your credentials are valid but lack permission for the specific operation. Authentication failures are permanent errors that require correcting your credentials, not transient issues that resolve with retries. The error typically results in an HTTP 401 status code, signaling that you need to provide valid, active credentials before the Inttegro API will process any aspect of your request.

## Example error response

```json
{
  "error": {
    "type": "bad_request",
    "cause": "authentication_failed",
    "code": "1401",
    "message": "authentication failed",
    "detail": "The request could not be authenticated. Ensure you are providing a valid API key in the Authorization header.",
    "fix_code": "change_request_parameters",
    "url": "https://studio.inttegro.com/e/1401"
  }
}
```

## Related errors

- [authorization\_failed](https://studio.inttegro.dev/machine/csharp/e/c-authorization_failed.md) - Valid credentials but insufficient permissions
- [bad\_request](https://studio.inttegro.dev/machine/csharp/e/t-bad_request.md) - Malformed request headers