n8n + ChatGPT: Build a Content Generation Automation in 20 Minutes

Before adding any nodes, store your OpenAI API key in n8n's Credentials vault. This way, every OpenAI node in every workflow can reuse the same key — you never paste it directly into a node.

Get your API key: log into platform.openai.com → API keys → Create new secret key. Copy it immediately — it won't be shown again.

Add to n8n: in your n8n instance, go to Settings → Credentials → Add Credential. Search for "OpenAI", select it, paste your API key, and save. Name it something you'll recognise ("OpenAI – main").

In n8n, go to Workflows → New. Click the "+" button on the canvas to add the first node. Search for "Webhook" and select it.

Webhook settings:

• HTTP Method: POST
• Path: content-brief (or any slug you prefer)
• Response Mode: Respond Immediately
• Response Data: First Entry JSON

Click Listen for Test Event — n8n will show a URL like https://your-n8n.com/webhook-test/content-brief. Keep this tab open.

Add a Set node after the Webhook. This node extracts and names the fields from the incoming request body, making the data easier to reference in later nodes.

In the Set node, add these fields (each mapped from the webhook body):

topic:     {{ $json.body.topic }}
audience: {{ $json.body.audience }}
tone:     {{ $json.body.tone }}
keywords: {{ $json.body.keywords }}

This assumes the POST body will look like:

{
  "topic":    "Best automation tools for small business",
  "audience": "small business owners, non-technical",
  "tone":     "practical, conversational",
  "keywords": "n8n, Zapier, Make, automation 2026"
}

Add an OpenAI node after Set. Connect it to your saved credential. Configure:

• Resource: Chat
• Operation: Complete
• Model: gpt-4o-mini (cheap and fast — upgrade to gpt-4o for higher quality)
• Max Tokens: 1200
• Temperature: 0.7

In the Messages section, add two messages:

Message 1 — System:

Role: system
You are a professional content writer specializing in B2B SaaS and
automation topics. You write in a clear, practical tone without
AI-giveaway phrases like "In conclusion", "Delve", or "It's worth
noting". Always return your response as valid JSON.

Message 2 — User:

Role: user
Write content for this brief:

Topic: {{ $json.topic }}
Target audience: {{ $json.audience }}
Tone: {{ $json.tone }}
Keywords to include: {{ $json.keywords }}

Return a JSON object with exactly these keys:
- "title": an H1 title (under 65 characters)
- "meta": a meta description (under 160 characters, includes main keyword)
- "intro": a 400-500 word blog introduction (first 2-3 paragraphs,
           no H1 heading, ends with a transition sentence)

Return ONLY the JSON object. No markdown fences, no extra text.

The OpenAI node returns the model's response as a string inside $json.message.content. Add a Code node (JavaScript) to parse it into a proper object.

// Code node — Run Once for All Items
const raw = $input.first().json.message.content;
const parsed = JSON.parse(raw);

return [{
  json: {
    title:    parsed.title,
    meta:     parsed.meta,
    intro:    parsed.intro,
    topic:    $input.first().json.topic    // pass through for Sheets
  }
}];

Add a Google Sheets node. Authenticate with your Google account. Set:

• Operation: Append or Update Row
• Spreadsheet: select or create your content calendar sheet
• Sheet: Sheet1 (or rename to "Drafts")

Map the columns. Your sheet should have headers in row 1:

Add a Slack node after Google Sheets. Authenticate with your Slack workspace and set:

• Operation: Post Message
• Channel: #content or your preferred channel

Message text:

📝 *New content draft ready*

*Title:* {{ $json.title }}
*Topic:* {{ $json.topic }}
*Meta:* {{ $json.meta }}

_Intro draft saved to Google Sheets ↗_

With the Webhook node in Listen for Test Event mode, send a test POST request. From your terminal:

curl -X POST https://your-n8n.com/webhook-test/content-brief \
  -H "Content-Type: application/json" \
  -d '{
    "topic":    "Best automation tools for small business 2026",
    "audience": "small business owners, non-technical",
    "tone":     "practical, conversational",
    "keywords": "n8n, Zapier, Make, automation"
  }'

Watch the n8n canvas — each node should highlight green as it executes. Check:

• OpenAI node output contains valid JSON with title, meta, intro
• Google Sheets has a new row appended
• Slack channel received the notification message

Once it works in test mode, click Activate in the top right. The workflow will now respond to POST requests on the production URL continuously.