Tool calling with generateObject and streamObject (structured outputs)

Issue

You may want to combine tool calling with structured output generation. While generateObject and streamObject are designed specifically for structured outputs, they don't support tool calling.

Background

To use tool calling with structured outputs, use generateText or streamText with the experimental_output option.

Important: When using experimental_output with tool calling, the structured output generation counts as an additional step in the execution flow.

Solution

When using experimental_output with tool calling, adjust your stopWhen condition to account for the additional step required for structured output generation:

const result = await generateText({
  model: openai('gpt-4o'),
  experimental_output: Output.object({
    schema: z.object({
      summary: z.string(),
      sentiment: z.enum(['positive', 'neutral', 'negative']),
    }),
  }),
  tools: {
    analyze: tool({
      description: 'Analyze data',
      inputSchema: z.object({
        data: z.string(),
      }),
      execute: async ({ data }) => {
        return { result: 'analyzed' };
      }),
    },
  },
  // Add at least 1 to your intended step count to account for structured output
  stopWhen: stepCountIs(3), // Now accounts for: tool call + tool result + structured output
  prompt: 'Analyze the data and provide a summary',
});

For more information about using structured outputs with generateText and streamText see Generating Structured Data.