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AI SDK by Vercel - build apps like ChatGPT, Claude, Gemini, and more with a single interface for any model using the Vercel AI Gateway or go direct to OpenAI, Anthropic, Google, or any other model provider.
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---
title: ToolChoiceViolationError
description: Learn how to fix AI SDK ToolChoiceViolationError
---
# ToolChoiceViolationError
This error occurs when a `generateText` or `streamText` response does not satisfy
an enforced tool choice. It is thrown when `toolChoice` is set to `'none'` but
the response contains a tool call, when `'required'` produces no structured tool
call, or when a specifically selected tool was not called. With `streamText`,
the error is emitted in the stream. Tool calls returned while `'none'` is selected
are not executed.
The error does not automatically interpret text or reasoning as an executable
tool call. When tool calls are allowed, you can inspect `content` to implement
opt-in recovery, including schema validation before executing any recovered call.
## Properties
- `toolChoice`: The effective tool choice that the response did not satisfy
- `finishReason`: The reason why the model finished generating the response
- `provider`: The provider that returned the response
- `modelId`: The model that returned the response
- `content`: The normalized content returned by the model
- `message`: The error message
## Checking for this Error
You can check if an error is an instance of `ToolChoiceViolationError` using:
```typescript
import { ToolChoiceViolationError } from 'ai';
if (
ToolChoiceViolationError.isInstance(error) &&
error.toolChoice.type !== 'none'
) {
const serializedCall = error.content.find(part => part.type === 'text')?.text;
// Parse and validate serializedCall before treating it as a tool call.
}
```