Build an AI Vendor Follow-Up Agent in n8n

Updated November 3, 2026. Built against the tool’s current screens and checked step by step. How we check this lesson

Chasing late purchase orders is a daily job in operations, and it usually lives in someone's head and inbox. In this free lesson you build an AI vendor follow-up agent in n8n for Ridgeline Supply Co. You give it a list of late or pending orders, it writes a polite, firm message for each one, and it logs every follow-up with a due date in Google Sheets.

Start here first: n8n AI Agent Tutorial: Save Social Media Ideas to Google Sheets. This Operations version follows the same build with its own example business, Ridgeline Supply Co.

Part of: AI for Operations Teams (step 22 of 40). Next up: A Support Agent That Answers from Your Own Docs

Build an AI Vendor Follow-Up Agent in n8n: video walkthrough

The whole lesson in 7:53, narrated step by step.

Simulated practice environment. Recorded in Stepthrough’s simulated practice environment, not the live tool. Practice it yourself free at learn.ynteractive.com.

▶7:53

7:53 · 12 chapters · 72 steps · narrated with the lesson’s own voice-over · Watch on YouTube

Chapters

Click a chapter to jump the video there.

1. 0:00 Intro: what you'll build
2. 0:11 Get n8n
3. 0:42 API key
4. 1:52 Chat trigger
5. 2:25 AI Agent
6. 2:40 System prompt
7. 3:19 Chat model
8. 4:07 Memory
9. 4:24 Sheets tool
10. 4:48 Create the spreadsheet
11. 5:34 Configure Sheets
12. 7:13 Test the agent

Now do it yourself, free

Watching is the warm-up. The interactive lesson puts you in a practice copy of n8n: you do every step yourself, it checks your work, and “Do it for me” finishes any step you get stuck on. Nothing touches your real accounts.

Practice “Build an AI Vendor Follow-Up Agent in n8n” step by step

Full transcript

Intro: what you'll build

0:00 Now we automate. You'll build an AI agent in n8n for Ridgeline Supply Company. It writes a follow-up for every late vendor order and saves each one to Google Sheets. Let's build it.

Get n8n

0:10 In the last lesson you built a Custom GPT that writes procedures. That is great for one person. But what if the AI wrote a follow-up for every late vendor order and logged it in a spreadsheet your team can track? That is what we are building now. First, you need an n8n account. Click get started free.

0:25 Type an email address. This is just practice, so anything works — it won't actually send anything.

0:31 Now click continue. In the real n8n, it sends you a six digit code, then asks for a name, a password, and an account name. Go do that in your own browser later, then come back and we will build.

API key

0:41 Your agent needs a brain, and that means an API key from OpenAI. Go to platform dot openai dot com — that is the developer side, not ChatGPT, and it bills completely separately. Before you make a key, put some money on the account. A brand new key with a zero balance just returns errors. Click add to credit balance. If you would rather not spend anything yet, n8n gives every new account free credits. In your own n8n, you can pick gateway credits on the model step and skip the key.

0:59 Ten dollars goes a very long way. You are charged per request, not per month, and each batch of follow-ups costs fractions of a cent. Click continue — in your own account it asks for a card at this point.

1:11 Balance sorted. Now go to API keys in the left menu.

1:14 Click create new secret key.

1:16 Name it after whatever is going to use it. Future you, staring at a list of forty keys, will thank you. I am calling this one n8n agent.

1:24 Default project, all permissions — that is fine for this. Create the key.

1:28 Now pay attention, because this is the only time you will ever see this key. Copy it and paste it into n8n, or into your password manager. If you lose it, you do not get it back — you delete it and make another.

1:40 Click done. One last warning — this key can spend your money. Never commit it to code, never paste it into a chat, and if it ever shows up on screen while you are recording, revoke it before you publish.

Chat trigger

1:52 Now you are inside n8n. This overview page lists every workflow you have. Top right, click create workflow, and you land on an empty canvas.

1:59 Every workflow needs a trigger — the thing that kicks it off. We want a chat trigger so you can tell the agent which orders are late or pending. Click add first step.

2:07 A panel slides in with every way a workflow can start — manually, on a schedule, on a webhook. We want on chat message, so we can have a conversation with the agent.

2:16 n8n opens the node so you can configure it. There is nothing we need to change here, so close it with the X in the top right and get back to the canvas.

AI Agent

2:24 Now we decide what happens when a message comes in. Click the plus on the right edge of the trigger.

2:29 There it is — AI Agent. This is the piece that can plan and then carry out actions using whatever tools you give it. You give it your open orders, and it can write the follow-ups and save them to a spreadsheet — all in one step.

System prompt

2:40 Right now this agent has no personality and no orders. It does not know it works for Ridgeline Supply. Scroll down to options and click add option.

2:49 Pick system message. This is the standing instruction the agent reads before every request. It is where we tell it who Ridgeline Supply is, how the messages should sound, and how to format them.

2:59 Here is the actual prompt. It describes Ridgeline Supply, sets a polite but firm tone, and tells the agent what to return: vendor, order, issue, follow-up message, and due date. It also tells the agent to use the Google Sheets tool when you ask it to save. Click paste system prompt.

3:14 That gives the agent everything it needs to know about Ridgeline Supply. Close the node.

Chat model

3:18 See that red triangle on the agent? It is complaining because it has no model. An agent can plan, but it cannot think without a language model underneath it. Click the plus under chat model.

3:28 OpenAI chat model. This is where that API key finally gets used.

3:32 And here is where that key you copied finally goes. Click the credential dropdown.

3:36 You want create new credential, right at the bottom. In your own n8n, if you skipped the key, you would pick gateway credits here instead.

3:39 Paste the key straight in. This is the one moment it matters that you copied it — remember, OpenAI never shows it to you again.

3:46 Hit save. n8n tests the connection straight away, and from now on this credential is available to every node in every workflow — you only do this once.

3:55 Now the model dropdown.

3:56 GPT five mini. Fast, cheap, and plenty for short follow-up messages. Do not reach for the expensive model until you have a reason.

4:04 That is the brain wired in. Close it up.

Memory

4:07 Next, memory. Without this, every message starts from nothing — you could not say save those follow-ups, because it would not remember which ones you meant. Click the plus under memory.

4:17 Simple memory is fine here — it keeps the recent conversation inside n8n, no database, no extra credentials.

Sheets tool

4:23 And now the good part — tools. This is what separates an agent from a chatbot. A chatbot just talks. An agent does things. We are going to give it Google Sheets so it can log every follow-up in a spreadsheet your team can track. Click the plus under tool.

4:37 Google Sheets tool. Now the agent can write rows into a real spreadsheet, with columns matching what the system prompt tells it to return. When you say save those follow-ups, each one becomes a row.

Create the spreadsheet

4:47 Before we set this up, we need to actually create the spreadsheet. Close this node for now — we are going to hop over to Google Sheets and make one.

4:54 Switch to Google Sheets. You need to create the spreadsheet that this node will write to.

4:58 First, name it so you can find it later. Click the title up top — it says untitled spreadsheet — and type Vendor Follow-Ups.

5:05 Now set up the column headers. These need to match what the system prompt tells the agent to return. In A1, type Vendor.

5:11 B1 — Order.

5:12 C1 — Issue.

5:14 D1 — Follow-up Message.

5:16 And E1 — Due Date. Five columns, matching exactly what the system prompt tells the agent to return. Each follow-up becomes a row in this sheet.

5:23 The spreadsheet is ready. Switch back to n8n and connect the Google Sheets node to it.

5:28 Double click the Google Sheets node to open it back up. Now we can connect it to the spreadsheet we just made.

Configure Sheets

5:33 Now we need to connect this to a real Google account. Click the credential dropdown.

5:38 Create new credential — this one uses Google OAuth instead of an API key, so it is going to open a sign-in window.

5:45 Click sign in with Google. This opens the Google account chooser so you can pick which account to connect.

5:51 Pick the Google account you want n8n to use. This is the account that owns the spreadsheet.

5:56 Google is asking what n8n is allowed to do. Check the first box — this lets n8n read and write your spreadsheets.

6:03 Second box — n8n needs Drive access so it can find your spreadsheets by name.

6:07 Last one — this lets Google connect to n8n as an external service. Check it.

6:12 All three checked. Click continue and Google hands the credential back to n8n.

6:17 Now we tell the node what to do. By default it reads rows, but we want to add rows. Click the operation dropdown.

6:23 Append row. Every follow-up the agent writes gets added as a new row at the bottom of the sheet.

6:29 Now pick the spreadsheet. Click the document dropdown.

6:32 Vendor Follow-Ups — the sheet we set up with columns for vendor, order, issue, message, and due date.

6:37 Now pick which tab inside that spreadsheet. Click the sheet dropdown.

6:41 Sheet one — it is the only tab, so this is simple.

6:44 Now the columns. Each column has a purple button — click it and the AI agent figures out what data goes there. Click the purple button next to Vendor.

6:52 Order. Same thing — click the purple button.

6:55 Issue.

6:56 Follow-up message.

6:57 And due date. Each one is now set to defined automatically by the model — the agent reads your column headers and figures out what goes where.

7:04 The sheets tool is fully wired up — credential, operation, spreadsheet, sheet, and column mapping. Close it and let us test this thing.

Test the agent

7:13 Everything is connected. Time to see if it works. Click open chat at the bottom of the canvas.

7:18 Give it your late and pending orders. Paste this prompt and see what comes back.

7:22 Send it off. The agent reads your system prompt and writes a follow-up for each order in the exact format you asked for.

7:28 Three follow-ups — a late order, a missing ship date, and a short shipment, each with one clear question and a reply-by date. Now tell it to save them. This is where the Google Sheets tool kicks in.

7:39 Send it. The agent uses the Google Sheets tool to write each follow-up as a row — vendor, order, issue, message, and due date.

7:47 Simple as that. We show you and you do it. Sign up below to learn AI automation for free.

Watch the 30-second version

2 short videos from this lesson. Watch, then do it yourself in the free practice copy.

▶0:32

n8n AI Agent: Give AI the rule, not the answer

Short with Robert · 0:32

n8n AI Agent tip: Give AI the rule, not the answer. You can ask ChatGPT to work out a date. An AI agent can do it for every row. Don't give it the dates, give it the rule: one line in the agent's instructions, "One…

Transcript

n8n AI Agent tip: Give AI the rule, not the answer. You can ask ChatGPT to work out a date. An AI agent can do it for every row. Don't give it the dates, give it the rule: one line in the agent's instructions, "One business day to reply if late. Two if pending." Add a Due Date column and the agent fills it in for each order. Same rule, every row, every time.

▶0:40

A chatbot talks. An agent does things.

Short · 0:40

A chatbot talks. An agent does things. For operations: build an AI agent in n8n that writes follow-ups for late or pending purchase orders, each with one clear question and a reply-by date, and saves them to Google…

Transcript

A chatbot talks. An agent does things. For operations: build an AI agent in n8n that writes follow-ups for late or pending purchase orders, each with one clear question and a reply-by date, and saves them to Google Sheets. Build it yourself, free, one click at a time: learn.ynteractive.com

Watch the full 7:53 video walkthrough

What you will build: an AI agent that chases late orders

You build a small n8n workflow with four parts: a chat trigger so you can talk to the agent, an AI Agent with a system prompt that knows Ridgeline Supply Co., an OpenAI chat model with simple memory, and a Google Sheets tool so it can write rows into a spreadsheet.

Then you test it. You paste three open orders: Tallpine Pallet Co. on PO 4471 is five days late, Corrugo Box Supply on PO 4480 has no ship date, and Northwind Wrap shipped PO 4492 twelve rolls short. The agent writes a short message for each. Every message names the PO, states the problem in one sentence, asks one clear question, and gives a reply-by date. When you say "save those follow-ups to the sheet", it writes each one as a row in a spreadsheet called Vendor Follow-Ups.

Who this is for

This lesson is for operations managers, purchasing coordinators and warehouse leads who spend part of every week asking vendors "where is my order?". You know the pain: a short shipment nobody logged, a ship date you were promised but never wrote down, a follow-up that went out late because the person who sends them was on the dock. No coding and no AI background are needed.

What the system prompt tells the agent

The system prompt is the standing instruction the agent reads before every request. It says who Ridgeline Supply Co. is: a small warehouse and distribution business that buys pallets, boxes, stretch wrap and janitorial supplies. It says who the messages are for: vendor sales reps and customer service teams.

It sets the tone as polite, plain, firm and brief, like an operations manager who values the relationship but needs an answer. It lists what each message must include, and it sets the reply-by rule: one business day if the order is late, two if it is pending. It also sets two limits. The agent may not threaten to cancel an order or invent penalties, and each message stays under 80 words. The five return fields match the five sheet columns exactly, which is why the Sheets tool knows where everything goes.

What you need

For the lesson itself, nothing but a browser. To build the agent for real you need an n8n account, an OpenAI API account with a small credit balance, and a Google account for Sheets. Keep the API key private: the lesson reminds you never to paste it into a chat, a shared file or a screen recording. Have a list of two or three real open orders ready so your first test is useful.

Why it works

A chatbot only talks. An agent can also act, and the Google Sheets tool is what lets it act. Memory lets you say "save those" and have it know which messages you meant. Because the model fills each column from your headers, you do not map fields by hand. The result is a running log of every vendor follow-up, with the issue and the date you expect an answer, in a sheet your whole team can see.

How to use this in your operation

Change the system prompt to describe your business, your usual vendors and your own reply-by rules. Each morning, paste the open POs from your purchasing report and let the agent draft the follow-ups. Review the messages, send them from your normal email, and use the Due Date column to see who owes you an answer today. Sort by vendor before a quarterly review and you have a clear record of who ships late and how often. The agent writes and logs; a person still decides what gets sent.

Step by step: Build an AI Vendor Follow-Up Agent in n8n

All 72 steps of the interactive module, in order. In the module you watch each one, then do it yourself in a practice copy that checks your work.

1. Get n8n

1. Go to n8n.io. Start at n8n.io. Click Get started free.

   In the last lesson you built a Custom GPT that writes procedures. That is great for one person. But what if the AI wrote a follow-up for every late vendor order and logged it in a spreadsheet your team can track? That is what we are building now. First, you need an n8n account.

2. Enter your email. Type any email address — this is practice, so a fake one is fine.

   This is just practice, so anything works — it won't actually send anything.

3. Sign up. Click Continue. n8n emails you a code, then asks for a name and password — do that part on your own and come back here.

   In the real n8n, it sends you a six digit code, then asks for a name, a password, and an account name. Go do that in your own browser later, then come back and we will build.

2. API key

4. Add credit first. Practice only: no card, no charge. Your agent needs a model to think with, and in the real world that is an OpenAI key with a little credit behind it. This is platform.openai.com → Billing. Click Add to credit balance. (Rather not spend anything later? New n8n accounts include free credits: pick Gateway credits on the model step instead of a key.)

   Your agent needs a brain, and that means an API key from OpenAI. Go to platform dot openai dot com — that is the developer side, not ChatGPT, and it bills completely separately. Before you make a key, put some money on the account. A brand new key with a zero balance just returns errors. If you would rather not spend anything yet, n8n gives every new account free credits. In your own n8n, you can pick gateway credits on the model step and skip the key.

5. Ten dollars is plenty. Ten dollars goes a long way — you pay per request, not per month. Click Continue. In your own account you add a card here.

   Ten dollars goes a very long way. You are charged per request, not per month, and each batch of follow-ups costs fractions of a cent.

6. Now the key. Balance sorted. Click API Keys in the left menu.

   Balance sorted. Now go to API keys in the left menu.

7. Create a secret key. Click + Create new secret key.
8. Name the key. Name it after what will use it. Type n8n agent.

   Name it after whatever is going to use it. Future you, staring at a list of forty keys, will thank you. I am calling this one n8n agent.

9. Create it. Leave Project and Permissions alone and click Create secret key.

   Default project, all permissions — that is fine for this. Create the key.

10. Copy it now. This is the only time OpenAI shows you the key. Click Copy, then paste it somewhere safe.

    Now pay attention, because this is the only time you will ever see this key. Copy it and paste it into n8n, or into your password manager. If you lose it, you do not get it back — you delete it and make another.

11. Back to n8n. Click Done. Treat that key like a password — never paste it into a chat, a repo, or a screen recording.

    One last warning — this key can spend your money. Never commit it to code, never paste it into a chat, and if it ever shows up on screen while you are recording, revoke it before you publish.

3. New workflow

12. Start a new workflow. This is your n8n home. Click Create workflow in the top right.

    Now you are inside n8n. This overview page lists every workflow you have. Top right, click create workflow, and you land on an empty canvas.

4. Chat trigger

13. Add the first step. Every workflow starts with a trigger. Click Add first step…

    Every workflow needs a trigger — the thing that kicks it off. We want a chat trigger so you can tell the agent which orders are late or pending.

14. Trigger on a chat message. The trigger panel opened on the right. Pick On chat message near the bottom.

    A panel slides in with every way a workflow can start — manually, on a schedule, on a webhook. We want on chat message, so we can have a conversation with the agent.

15. Back to the canvas. n8n opens the node so you can configure it. Nothing to change here — click the × in the top right.

    n8n opens the node so you can configure it. There is nothing we need to change here, so close it with the X in the top right and get back to the canvas.

5. AI Agent

16. Add the next node. Click the + on the right edge of the trigger node.

    Now we decide what happens when a message comes in.

17. Open the AI nodes. The What happens next? panel opens with categories. Click AI at the top.

    A panel opens and asks what happens next. The agent lives under AI, right at the top.

18. Add the AI Agent. In AI Nodes, click AI Agent — it makes a plan and carries it out using the tools you give it.

    There it is — AI Agent. This is the piece that can plan and then carry out actions using whatever tools you give it. You give it your open orders, and it can write the follow-ups and save them to a spreadsheet — all in one step.

6. System prompt

19. Open the options. The agent has no personality yet. Click + Add Option under Options.

    Right now this agent has no personality and no orders. It does not know it works for Ridgeline Supply.

20. Add a system message. Choose System Message. This is the standing instruction the agent follows every time.

    Pick system message. This is the standing instruction the agent reads before every request. It is where we tell it who Ridgeline Supply is, how the messages should sound, and how to format them.

21. Write the system prompt. The box starts with You are a helpful assistant. Replace it with the standing instruction: it is long, so just Paste in the system prompt on the box.

    Here is the actual prompt. It describes Ridgeline Supply, sets a polite but firm tone, and tells the agent what to return: vendor, order, issue, follow-up message, and due date. It also tells the agent to use the Google Sheets tool when you ask it to save.

    You are the purchasing follow-up assistant for Ridgeline Supply Co.
    
    Ridgeline Supply Co. is a small warehouse and distribution business that buys pallets, boxes, stretch wrap and janitorial supplies from vendors and ships them to local businesses.
    
    The audience is vendor sales reps and customer service teams.
    
    The tone should be polite, plain, firm and brief. Sound like an operations manager who values the relationship but needs an answer.
    
    Your job is to write a follow-up message for each late or pending purchase order the user gives you.
    
    For each message:
    - Name the PO number and what was ordered
    - State the problem in one sentence
    - Ask one clear question: a ship date, a tracking number, or a fix
    - Give a reply-by date: 1 business day if late, 2 if pending
    
    For each follow-up, return:
    - Vendor
    - Order
    - Issue
    - Follow-up Message
    - Due Date
    
    When the user asks you to save the follow-ups, use the Google Sheets tool to store each one.
    
    Do not threaten to cancel orders or invent penalties. Keep each message under 80 words.

22. Back to the canvas. That tells the agent who it works for and how to write follow-ups. Close the node with the ×.

    That gives the agent everything it needs to know about Ridgeline Supply. Close the node.

7. Chat model

23. Give the agent a brain. The agent has a red warning: it has no model. Click the + under Chat Model.

    See that red triangle on the agent? It is complaining because it has no model. An agent can plan, but it cannot think without a language model underneath it.

24. Pick OpenAI. Click OpenAI Chat Model.

    OpenAI chat model. This is where that API key finally gets used.

25. Open the credentials. Here is where that key goes. Click the Credential dropdown.

    And here is where that key you copied finally goes.

26. Create a new credential. Click + Create new credential at the bottom of the list. (Free credits instead? Pick Gateway credits in your own n8n.)

    You want create new credential, right at the bottom. In your own n8n, if you skipped the key, you would pick gateway credits here instead.

27. Paste the key. Paste in the API key on the field to drop in the key you copied from OpenAI.

    This is the one moment it matters that you copied it — remember, OpenAI never shows it to you again.

28. Save the credential. Click Save. n8n tests the connection and stores the key for every future node.

    n8n tests the connection straight away, and from now on this credential is available to every node in every workflow — you only do this once.

29. Open the model list. A new credential leaves Model on Select a model.... Click the Model dropdown.

    Now the model dropdown.

30. Choose the model. Pick gpt-5-mini — fast and cheap, plenty for this. (The list is long: type gpt-5-mini in Search... to find it.)

    GPT five mini. Fast, cheap, and plenty for short follow-up messages. Do not reach for the expensive model until you have a reason.

31. Back to the canvas. The model is wired up. Close the node with the ×.

    That is the brain wired in. Close it up.

8. Memory

32. Add memory. Without memory the agent forgets each message. Click the + under Memory.

    Next, memory. Without this, every message starts from nothing — you could not say save those follow-ups, because it would not remember which ones you meant.

33. Simple Memory. Pick Simple Memory. It keeps the recent conversation in n8n itself.

    Simple memory is fine here — it keeps the recent conversation inside n8n, no database, no extra credentials.

34. Back to the canvas. n8n opens Simple Memory so you can set it up. The defaults are fine (it keeps the last 5 messages). Close it with the ×.

    n8n opens simple memory so you can set it up. The defaults are fine. It keeps the last five messages. Close it with the X.

9. Sheets tool

35. Add a tool. Tools are how the agent acts on the world. Click the + under Tool.

    And now the good part — tools. This is what separates an agent from a chatbot. A chatbot just talks. An agent does things. We are going to give it Google Sheets so it can log every follow-up in a spreadsheet your team can track.

36. Search for Sheets. Google Sheets is not in Recommended Tools. In Search nodes..., type sheets.

    Google Sheets is not in the recommended tools, so search for it.

37. Add Google Sheets. Click Google Sheets Tool — read, update and write data to Google Sheets.

    Google Sheets tool. Now the agent can write rows into a real spreadsheet, with columns matching what the system prompt tells it to return. When you say save those follow-ups, each one becomes a row.

10. Create the spreadsheet

38. Back to the canvas. Before we configure this node, we need a spreadsheet for the agent to write to. Close the node — we will come back.

    Before we set this up, we need to actually create the spreadsheet. Close this node for now — we are going to hop over to Google Sheets and make one.

39. Open Google Sheets. Click the Google Sheets tab to create a new blank spreadsheet.

    Switch to Google Sheets. You need to create the spreadsheet that this node will write to.

40. Name the spreadsheet. Click the title and rename it to Vendor Follow-Ups.

    First, name it so you can find it later.

41. Type the first column header. In cell A1, type Vendor.

    Now set up the column headers. These need to match what the system prompt tells the agent to return. In A1, type Vendor.

42. Order. In cell B1, type Order.

    B1 — Order.

43. Issue. In cell C1, type Issue.

    C1 — Issue.

44. Follow-up Message. In cell D1, type Follow-up Message.

    D1 — Follow-up Message.

45. Due Date. In cell E1, type Due Date. That is all five columns — matching the system prompt.

    And E1 — Due Date. Five columns, matching exactly what the system prompt tells the agent to return. Each follow-up becomes a row in this sheet.

46. Back to n8n. The spreadsheet is ready. Click the n8n tab to go back and connect it.

    The spreadsheet is ready. Switch back to n8n and connect the Google Sheets node to it.

47. Open the Sheets node. Double-click the Google Sheets node (n8n named it Get row(s) in sheet in Google Sheets) to configure it.

    Double click the Google Sheets node to open it back up. Now we can connect it to the spreadsheet we just made.

11. Configure Sheets

48. Add a credential. The Sheets node needs a Google account. Click the Credential dropdown.

    Now we need to connect this to a real Google account.

49. Create a new credential. Click + Create new credential to sign in with Google.

    Create new credential — this one uses Google OAuth instead of an API key, so it is going to open a sign-in window.

50. Sign in with Google. Click Sign in with Google to connect your account.

    This opens the Google account chooser so you can pick which account to connect.

51. Choose your account. Click your Google account to continue.

    Pick the Google account you want n8n to use. This is the account that owns the spreadsheet.

52. Allow Sheets access. Google needs permission. Check See, edit, create, and delete all your Google Sheets spreadsheets.

    Google is asking what n8n is allowed to do. Check the first box — this lets n8n read and write your spreadsheets.

53. Allow Drive access. Check See, edit, create, and delete all of your Google Drive files.

    Second box — n8n needs Drive access so it can find your spreadsheets by name.

54. Allow external service. Check Connect to an external service.

    Last one — this lets Google connect to n8n as an external service. Check it.

55. Sign in. All three are checked. Click Continue to complete the Google sign-in.

    All three checked.

56. Pick the operation. Now tell n8n what to do with the sheet. Click the Operation dropdown.

    Now we tell the node what to do. By default it reads rows, but we want to add rows.

57. Append Row. Pick Append Row — the agent will add a new row for each follow-up.

    Append row. Every follow-up the agent writes gets added as a new row at the bottom of the sheet.

58. Choose the spreadsheet. Click the Document dropdown to pick which spreadsheet to write to.

    Now pick the spreadsheet.

59. Vendor Follow-Ups. Click Vendor Follow-Ups — the sheet we set up for Ridgeline.

    Vendor Follow-Ups — the sheet we set up with columns for vendor, order, issue, message, and due date.

60. Pick the sheet tab. Click the Sheet dropdown to choose which tab inside the spreadsheet.

    Now pick which tab inside that spreadsheet.

61. Sheet1. Click Sheet1.

    Sheet one — it is the only tab, so this is simple.

62. Map the Vendor column. Under Values to Send, click the ✦ button next to Vendor — the AI agent will fill this in automatically.

    Now the columns. Each column has a purple button — click it and the AI agent figures out what data goes there.

63. Map the Order column. Click the ✦ button next to Order.

    Order. Same thing — click the purple button.

64. Map the Issue column. Click the ✦ button next to Issue.

    Issue.

65. Map the Follow-up Message column. Click the ✦ button next to Follow-up Message.

    Follow-up message.

66. Map the Due Date column. Click the ✦ button next to Due Date.

    And due date. Each one is now set to defined automatically by the model — the agent reads your column headers and figures out what goes where.

67. Back to the canvas. Google Sheets is fully configured. Close the node with the ×.

    The sheets tool is fully wired up — credential, operation, spreadsheet, sheet, and column mapping. Close it and let us test this thing.

12. Test the agent

68. Open the chat. Time to test. Click Open chat at the bottom of the canvas.

    Everything is connected. Time to see if it works.

69. Ask for follow-ups. Type a prompt — give the agent your late and pending orders.

    Give it your late and pending orders.

    Write follow-ups: Tallpine Pallet Co., PO 4471, 5 days late. Corrugo Box Supply, PO 4480, no ship date. Northwind Wrap, PO 4492, 12 rolls short.

70. Send the message. Click the send arrow to talk to the agent.

    Send it off. The agent reads your system prompt and writes a follow-up for each order in the exact format you asked for.

71. Save to the sheet. Now tell the agent to save those follow-ups to Google Sheets.

    Three follow-ups — a late order, a missing ship date, and a short shipment, each with one clear question and a reply-by date. Now tell it to save them. This is where the Google Sheets tool kicks in.

72. Send it. Click the send arrow — the agent will use the Google Sheets tool to write the rows.

    Send it. The agent uses the Google Sheets tool to write each follow-up as a row — vendor, order, issue, message, and due date.

More videos from this lesson

▶1:09

n8n AI Agent – AI Vendor Follow-Up Agent for operations teams: the 1-minute version

Highlight · 1:09 · with captions

n8n AI Agent tip: For operations: build an AI agent in n8n that writes follow-ups for late or pending purchase orders, each with one clear question and a reply-by date, and saves them to Google Sheets.

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Screenshots

Frequently asked questions

Does the agent email vendors by itself?

Not in this lesson. It writes the follow-up messages and logs them in Google Sheets. You review and send them. The next lesson in this section shows how to add a Gmail tool so an agent can send email.

Is this lesson free?

Yes, Stepthrough is completely free. To build the agent for real you need your own n8n account and an OpenAI API account. OpenAI charges per request; the lesson adds a $10 credit balance, and short messages like these cost a fraction of a cent each. n8n has its own plans, so check its current pricing.

Do I need to know how to code?

No. Every node is added by clicking, and the system prompt is pasted in for you. The lesson is 69 short steps and about 12 minutes.

Can I change the spreadsheet columns?

Yes. Keep the column headers and the fields listed in the system prompt the same, and the agent will fill whatever columns you set up.

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.

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