ToolChoiceViolationError

This error occurs when a generateText response does not satisfy an enforced tool choice. It is thrown when toolChoice is set to 'required' but the response contains no structured tool call, or when a specifically selected tool was not called.

The error does not automatically interpret text or reasoning as an executable tool call. 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:

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import { ToolChoiceViolationError } from 'ai';
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if (ToolChoiceViolationError.isInstance(error)) {
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  const serializedCall = error.content.find(part => part.type === 'text')?.text;
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  // Parse and validate serializedCall before treating it as a tool call.
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}