Errors

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HTTP errors

Our API follows a predictable HTTP error code format:

• 400 - invalid_request_error: There was an issue with the format or content of your request. We may also use this error type for other 4XX status codes not listed below.
• 401 - authentication_error: There’s an issue with your API key.
• 403 - permission_error: Your API key does not have permission to use the specified resource.
• 404 - not_found_error: The requested resource was not found.
• 413 - request_too_large: Request exceeds the maximum allowed number of bytes.
• 429 - rate_limit_error: Your account has hit a rate limit.
• 500 - api_error: An unexpected error has occurred internal to Anthropic’s systems.
• 529 - overloaded_error: Anthropic’s API is temporarily overloaded.

When receiving a streaming response via SSE, it’s possible that an error can occur after returning a 200 response, in which case error handling wouldn’t follow these standard mechanisms.

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Error shapes

Errors are always returned as JSON, with a top-level error object that always includes a type and message value. For example:

{
  "type": "error",
  "error": {
    "type": "not_found_error",
    "message": "The requested resource could not be found."
  }
}

In accordance with our versioning policy, we may expand the values within these objects, and it is possible that the type values will grow over time.

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Request id

Every API response includes a unique request-id header. This header contains a value such as req_018EeWyXxfu5pfWkrYcMdjWG. When contacting support about a specific request, please include this ID to help us quickly resolve your issue.