InvalidToolArgumentsError unhandled by useChat, leading to infinite loop

[BrianHung]

InvalidToolArgumentsError unhandled by useChat, leading to infinite loop

[lgrammel]

WIP PR: #2052

[BrianHung]

A possible solution might be to enqueue a toolCall message and the error message, so that useChat gets an updated messages list which prevents triggerRequest from being called again.

          } catch (error) {
            controller.enqueue // tool call finished with an arguments parsing error
            toolResultsStreamController!.enqueue({
              type: 'error',
              error,
            });
          }

ai/packages/core/core/generate-text/run-tools-transformation.ts

Lines 118 to 123 in 0565cd7

	} catch (error) {
	toolResultsStreamController!.enqueue({
	type: 'error',
	error,
	});
	}

[BrianHung]

If I am reading this right

Unfortunately function-calling is not guaranteed to follow the schema, and there can be differences in quality from model to model.

The arguments returned may not always follow the zod schema that was given.

I don't know what is better behavior here

• stop early and tell the user that it was unable to generate arguments to the specified tool call
• continue to try again until maxAutomaticRoundtrips is exhausted

[BrianHung]

For my use case, I was able to avoid an argument parsing error by being more precise with the tool and parameter descriptions.

showBarChart: {
	description:
		'Make a bar plot in matplotlib. The bars are positioned at x. Their dimensions are given by height. Always include the data parameter as a list of JSON objects.',
	parameters: z.object({
		axisKey: z.string().describe('The key to use for the x-axis.'),
		data: z
			.array(z.record(z.union([z.string(), z.number()])))
			.describe(
				'List of JSON objects for which to generate grouped bars. JSON objects must always contain axisKey as a field.'
			),
		title: z.string().optional().describe('Set a title for the plot.'),
		yLabel: z.string().optional().describe('Set the label for the y-axis.'),
	}),
},

[lgrammel]

Reproduced.

[lgrammel]

Cause:

• when the last message in useChat is an assistant message with completed tool calls,
• and streamText only returns an error event,
• then the checks fail and an infinite loop with the last assistant message is started.