Fireworks AI Tool Schema Rejection with drop_params Not Sanitizing Nested Schemas

What this error means

Fireworks AI rejects tool schemas with 'default': null and 'title' in JSON Schema properties is a LiteLLM failure pattern reported for developers trying to fix fireworks ai tool call failures when json schema properties contain default:null and title fields that drop_params doesn’t sanitize. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Open issue on BerriAI/litellm. Fireworks AI rejects tool schemas containing ‘default’: null and ‘title’ in JSON Schema properties. drop_params: true doesn’t sanitize nested schemas. Affects Claude Code + Kimi K2 workflows.

Common causes

• Developers using Claude Code with Kimi K2 via Fireworks AI through LiteLLM get tool call failures. The drop_params setting doesn’t sanitize nested schema properties, breaking tool-using workflows.
• Open issue on BerriAI/litellm. Fireworks AI rejects tool schemas containing ‘default’: null and ‘title’ in JSON Schema properties. drop_params: true doesn’t sanitize nested schemas. Affects Claude Code + Kimi K2 workflows.

Quick fixes

1. Confirm the exact error signature matches Fireworks AI rejects tool schemas with 'default': null and 'title' in JSON Schema properties.
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/BerriAI/litellm/issues/27821

Evidence note: Open issue on BerriAI/litellm. Fireworks AI rejects tool schemas containing ‘default’: null and ‘title’ in JSON Schema properties. drop_params: true doesn’t sanitize nested schemas. Affects Claude Code + Kimi K2 workflows.

Related errors

• LiteLLM drop_params nested schema
• Fireworks AI tool schema validation
• LiteLLM JSON Schema sanitization

FAQ

What should I check first?

Start with the exact Fireworks AI rejects tool schemas with 'default': null and 'title' in JSON Schema properties 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 Fireworks AI rejects tool schemas with 'default': null and 'title' in JSON Schema properties.