ToolLoopAgent error handling

ToolLoopAgent.ts

import { google } from '@ai-sdk/google'
import { ToolLoopAgent } from 'ai'
import { z } from 'zod'

const triggerSchema = z.object({
  trigger: z.string().describe('any string to trigger')
})

const tools = {
  flakyTool: {
    description: 'Very high chance it fails, but lets try it',
    parameters: triggerSchema,
    execute: async ({ trigger }: { trigger: string }) => {
      console.log('flakyTool called with:', trigger)
      throw new Error('nope')
    }
  },
  fallbackTool: {
    description: 'Always works, unlike my first startup',
    parameters: triggerSchema,
    execute: async ({ trigger }: { trigger: string }) => {
      console.log('fallbackTool called with:', trigger)
      return 'fallback success'
    }
  }
}

const agentWithThrow = new ToolLoopAgent({
  model: google('gemini-3-flash-preview'),
  instructions:
    'You are a helpful assistant. When a tool fails, try using a fallback tool.',
  tools,
  maxSteps: 5
})

const resultWithThrow = await agentWithThrow.generate({
  prompt: 'Try the flaky tool, if it fails then call the fallback tool'
})

console.log('Result:', resultWithThrow.text)
console.log('Steps:', resultWithThrow.steps.length)



const toolsNoThrow = {
  flakyTool: {
    description: 'Very high chance it fails, but lets try it',
    parameters: triggerSchema,
    execute: async ({ trigger }: { trigger: string }) => {
      console.log('flakyTool called with:', trigger)
      return { success: false, message: 'flaky failure' }
    }
  },
  fallbackTool: {
    description: 'Always works, unlike my first startup',
    parameters: triggerSchema,
    execute: async ({ trigger }: { trigger: string }) => {
      console.log('fallbackTool called with:', trigger)
      return 'fallback success'
    }
  }
}

const agentNoThrow = new ToolLoopAgent({
  model: google('gemini-3-flash-preview'),
  instructions:
    'You are a helpful assistant. When a tool returns success: false, try using a fallback tool.',
  tools: toolsNoThrow,
  maxSteps: 5
})

const resultNoThrow = await agentNoThrow.generate({
  prompt: 'Try the flaky tool, if it fails then call the fallback tool'
})

console.log('Result:', resultNoThrow.text)
console.log('Steps:', resultNoThrow.steps.length)
process.exit(0)


/* 
flakyTool called with: undefined
fallbackTool called with: undefined
Result: The flaky tool failed, so I called the fallback tool, which succeeded.
Steps: 3
flakyTool called with: undefined
fallbackTool called with: undefined
Result: The flaky tool failed as expected, so I have successfully called the fallback tool.
Steps: 3

*/