Debug AI Agent Tool Calls with OpenRouter, Calculator & Webhook

Debug tool calls in your n8n AI support agent—using Calculator, a simulated Order Lookup, and an incoming Webhook

This n8n workflow helps you verify whether your AI Agent correctly calls tools, by comparing a correct arithmetic result, a found order response, and an empty order lookup that can still “succeed.” It’s Exercise 4 from the n8n Production AI Playbook on Audit & Trace.

What this workflow does

• Receives a POST Webhook with a natural-language query.
• Runs “Support Agent”, an AI Agent using an OpenRouter chat model, which decides whether to call a tool.
• Uses the Calculator tool to handle arithmetic questions (e.g., “47 times 89”).
• Uses the Order Lookup Tool to return a simulated order record, or an empty string when the order does not exist—useful for tracing “empty lookup” behaviors.
• Responds back to the webhook caller with the agent’s final answer.

Use cases

• Audit & Trace tool calling: confirm the agent calls Calculator for math and Order Lookup for order questions.
• Detect misleading “success”: compare replies when an order lookup returns an empty value (e.g., ORD-8888) versus a found record (e.g., ORD-1001).
• Support automation QA: validate end-to-end behavior before deploying a tool-using agent in production.

Technical details

• n8n nodes: webhook, n8nn8n-nodes-langchainagent (Support Agent), respond to webhook, and tool nodes including n8nn8n-nodes-langchaintool code and n8nn8n-nodes-langchaintool calculator.
• OpenRouter integration: add an OpenRouter API credential to “OpenRouter - Agent” and choose a model that supports tool calling.
• Optional tracing: enable OpenTelemetry tracing in Settings > OpenTelemetry to view spans per tool call.

Quick setup & customization

Test via the Webhook Test URL using queries like {"query":"What is 47 times 89?"} and {"query":"How much was order ORD-8888? Tell the customer the amount."}. For clearer outcomes, you can customize the Order Lookup Tool to return "No order found" instead of an empty string.