LiteLLM APIResponseValidationError: Malformed output_schema Causes Provider to Reject Request

What this error means

LiteLLM APIResponseValidationError — malformed output_schema causes provider rejection is a LiteLLM failure pattern reported for developers trying to fix litellm apiresponsevalidationerror when output_schema is malformed. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

When output_schema contains typos (e.g., ‘intger’ instead of ‘integer’), LiteLLM forwards the request to the provider which rejects it with APIResponseValidationError. Error surfaces as LLMResponseParseError with no clear guidance.

Common causes

• Malformed JSON Schema in output_schema causes LiteLLM to throw APIResponseValidationError instead of catching the error early, wasting API calls and producing unclear error messages
• When output_schema contains typos (e.g., ‘intger’ instead of ‘integer’), LiteLLM forwards the request to the provider which rejects it with APIResponseValidationError. Error surfaces as LLMResponseParseError with no clear guidance.

Quick fixes

1. Confirm the exact error signature matches LiteLLM APIResponseValidationError — malformed output_schema causes provider rejection.
2. Check the LiteLLM account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/spinje/pflow/issues/388

Evidence note: When output_schema contains typos (e.g., ‘intger’ instead of ‘integer’), LiteLLM forwards the request to the provider which rejects it with APIResponseValidationError. Error surfaces as LLMResponseParseError with no clear guidance.

Related errors

• LiteLLM rate limit error
• OpenAI API context length exceeded

FAQ

What should I check first?

Start with the exact LiteLLM APIResponseValidationError — malformed output_schema causes provider rejection text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed LiteLLM workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without LiteLLM APIResponseValidationError — malformed output_schema causes provider rejection.