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Google Gemini API error

Gemini API 400 parameter_unknown: what it means and how to fix it

Error message
400 parameter_unknown

Retry? NoLast verified 2 documented fixes2 sources

What it means

The request contains a parameter the API does not recognize.

Causes

  • An unknown or unsupported parameter in the request body

How to fix it

  1. Fix 1.

    Remove the unrecognized parameter and send the request again.

  2. Fix 2.

    Make sure you are using the correct API version (for example /v1 or /v1beta); Beta features are only available in /v1beta.

More Gemini API errors

All 30 Gemini API errors

HTTP 400 at other providers

Compare 400 across providers

FAQ

What does the Gemini API error "400 parameter_unknown" mean?

The request contains a parameter the API does not recognize.

How do I fix Gemini API "400 parameter_unknown"?

There are 2 documented fixes. Start with the first: Remove the unrecognized parameter and send the request again.

Should I retry Gemini API "400 parameter_unknown"?

No. The official docs treat this error as not retryable: fix the cause before sending the request again.

Which other AI APIs return HTTP 400?

Per their official error docs: Amazon Bedrock (400 ValidationException; 400 ServiceQuotaExceededException; 400 IncompleteSignature; 400 InvalidAction; 400 NotAuthorized; 400 RequestExpired), Anthropic API (400 invalid_request_error; 400 invalid_request_error (spend limit reached)), Azure OpenAI (400 Bad Request; 400 content_filter), Cohere API (400 Bad Request; 400 Bad Request (too many tokens)), DeepSeek API (400 - Invalid Format), Groq API (400 Bad Request), Mistral API (400 Bad request), OpenAI API (400 invalid_request_error (Invalid service_tier argument); 400 BadRequestError), OpenRouter (400 invalid_request; 400 invalid_prompt; 400 context_length_exceeded; 400 max_tokens_exceeded; 400 token_limit_exceeded; 400 string_too_long; 400 invalid_image; 400 image_too_large; 400 image_too_small; 400 unsupported_image_format; 400 image_download_failed), Vertex AI (400 INVALID_ARGUMENT / FAILED_PRECONDITION), xAI API (400 Bad Request).

Sources

Last verified against 2 sources: Gemini API's official docs and official SDK repositories.

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