Vercel AI SDK OpenAI-Compatible Provider Tool Calls Fail with Missing type object in JSON Schema

What this error means

Invalid schema for function 'functionName': schema must be a JSON Schema of 'type: "object"', got 'type: null' is a Vercel AI SDK failure pattern reported for developers trying to fix tool call failures when using deepseek or other openai-compatible providers with vercel ai sdk. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Official Vercel AI SDK issue #7924 with 10+ comments. Root cause identified in provider-utils/schema.ts — asSchema() produces schemas without type: object. Multiple PRs (12283, 15163, 15249) attempted fixes. Affects all OpenAI-compatible providers that strictly validate JSON Schema.

Common causes

• Developers using Vercel AI SDK with non-OpenAI providers (DeepSeek, local LLMs) encounter tool call failures because the SDK generates tool schemas without explicit type: object. This blocks production AI app deployments that rely on cost-effective alternative providers.
• Official Vercel AI SDK issue #7924 with 10+ comments. Root cause identified in provider-utils/schema.ts — asSchema() produces schemas without type: object. Multiple PRs (12283, 15163, 15249) attempted fixes. Affects all OpenAI-compatible providers that strictly validate JSON Schema.

Quick fixes

1. Confirm the exact error signature matches Invalid schema for function 'functionName': schema must be a JSON Schema of 'type: "object"', got 'type: null'.
2. Check the Vercel AI SDK account, local tool state, and provider configuration involved in the failing workflow.
3. Check the build output, project root, and deployment platform configuration before redeploying.

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/vercel/ai/issues/7924
• https://github.com/vercel/ai/pull/12283

Evidence note: Official Vercel AI SDK issue #7924 with 10+ comments. Root cause identified in provider-utils/schema.ts — asSchema() produces schemas without type: object. Multiple PRs (12283, 15163, 15249) attempted fixes. Affects all OpenAI-compatible providers that strictly validate JSON Schema.

Related errors

• Vercel AI SDK tool call timeout with self-hosted models
• OpenAI provider JSON response parsing error

FAQ

What should I check first?

Start with the exact Invalid schema for function 'functionName': schema must be a JSON Schema of 'type: "object"', got 'type: null' text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Vercel AI SDK 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 Invalid schema for function 'functionName': schema must be a JSON Schema of 'type: "object"', got 'type: null'.