Build an n8n AI Agent That Writes Deal Follow-Ups

A Custom GPT helps with one email at a time. In this free lesson you build an AI agent in n8n for Northwind Scheduling Software that takes a list of open deals, writes a follow-up matched to each deal's stage, and saves every message to a Google Sheet your team can review before anything goes out.

What you will build: an AI agent for your open deals

You build a small n8n workflow: a chat trigger, an AI Agent with a system prompt, an OpenAI chat model, simple memory, and a Google Sheets tool. Then you test it with three real-sounding deals: Maria Lopez at Maple Row Cleaning, who had a demo today; Sam Patel at Fernhill Lawn Care, whose trial ends Friday; and Jen Walsh at Birch Lane Grooming, who went quiet after seeing pricing.

The agent writes a different message for each one. Maria gets a recap that ties the shared calendar to her double-booked cleaners and an offer to set up a trial. Sam gets a short check-in before his trial ends. Jen gets a no-pressure note about the smaller Starter plan. When you say 'save those follow-ups to the sheet', the agent writes one row per deal into a spreadsheet called Deal Follow-Ups.

What you need

Nothing, to take the lesson. The whole build runs in a practice copy in your browser. To build it for real afterwards you need an n8n account, an OpenAI API account with a small amount of credit (the lesson adds $10, which goes a long way for short messages), and a Google account for the spreadsheet. Have a few open deals in mind, with the stage each one is in, so you can test it with your own pipeline.

Who this is for

This lesson is for sales reps with a full pipeline, sales managers who want follow-ups that sound the same across the team, and sales ops people looking for a first, simple automation. You do not need to code. You will need your own n8n, OpenAI and Google accounts to build it for real later.

Step by step: what you do in the lesson

• Get n8n: start a free n8n account.
• API key: add $10 of credit on the OpenAI platform, create a secret key, name it and copy it.
• New workflow and chat trigger: start a workflow and trigger it on a chat message.
• AI Agent and system prompt: add the AI Agent, open Options, add a system message and paste the Northwind follow-up prompt.
• Chat model: add the OpenAI chat model, save your key as a credential and choose gpt-5-mini.
• Memory: add Simple Memory so the agent remembers which follow-ups you mean.
• Sheets tool: add the Google Sheets tool.
• Create the spreadsheet: name it Deal Follow-Ups and type five headers: Prospect, Company, Stage, Follow-up Message, Next Step.
• Configure Sheets: sign in with Google, pick Append Row, choose the spreadsheet and Sheet1, and click the button next to each column so the model fills it.
• Test the agent: open the chat, paste your open deals, then ask it to save the follow-ups.

What the system prompt tells the agent

The system prompt says who the agent works for and who it writes to: owners and office managers who are talking to Northwind's sales team. It sets a friendly, plain and specific tone, and says to sound like a helpful rep, not a pushy one. For each deal it returns five things that match the five sheet columns. Each message fits the deal's stage, stays under 80 words and ends with one clear ask. It never invents prices, discounts or results.

Why it works

The system prompt does the job a sales playbook does for a new hire, and the Sheets tool turns a chat into a record. Because the spreadsheet columns match what the prompt returns, the agent knows where each piece goes. Memory lets you work in plain language: ask for follow-ups, read them, then say 'save those'. Nothing is sent to a prospect automatically. Every message lands in a sheet first, so a rep or manager can check it.

How to use this in your sales process

Swap the Northwind details for your own product, plans and tone, and change the columns to fit how your team works. Paste a list of deals from your pipeline review each morning, or the deals that have not been touched in a week, and get a draft follow-up for every one. The sheet doubles as a simple follow-up log you can sort by stage. Later you could add a schedule trigger or connect your CRM, but the version in this lesson is the right place to start.

Frequently asked questions

How does the interactive lesson work?

Each step is shown to you first on the left (Watch). Then you do it yourself in a practice copy on the right (Your turn), and every click is checked. If you get stuck, press Do it for me. It is a practice copy, so no real accounts are touched.

Is this free?

Stepthrough is completely free. To build the agent for real you need your own n8n account, an OpenAI API account with some credit, and a Google account. Those tools may cost money to use, though short follow-ups on gpt-5-mini cost fractions of a cent each.

Does the agent send emails to my prospects?

No. In this lesson the agent only writes follow-ups and saves them to Google Sheets, so a person reviews each one before anything is sent.

Do I need to know how to code?

No. You build the whole workflow by clicking and pasting in n8n. The system prompt is plain English.

Can I connect it to my CRM?

n8n connects to many CRMs, but this lesson uses a chat trigger and Google Sheets to keep the first build simple. You can swap in other nodes once it works.

More in AI Automation for Sales