Generate and Auto-Evaluate Facebook Ad Headlines using GPT-4o-mini

Description

Generate and Auto-Evaluate Facebook Ad Headlines using GPT-4o-mini

Built with n8n + OpenAI

This workflow captures a product description, generates ad headlines, evaluates them with custom criteria, decides whether another draft is needed, and finally sends the best version via Gmail.

⚡ Section 1: Capture the Brief & Build the Prompt

📝 FormTrigger\_CopywritingBrief* → A simple form asks: *“What is your product about?”
⚙️ Set\_PromptForHeadline** → Prepares the input by appending the instruction:
“Write a Facebook ad headline for this product:”

Benefit: Ensures consistent, structured prompts so the AI receives clear context every time.

✍️ Section 2: Draft the Headline

💬 LLM\_HeadlineWriterModel** → GPT-4o-mini model provides the intelligence.
✍️ Agent\_HeadlineWriter** → Generates a first-pass Facebook ad headline.

Benefit: Produces creative copy instantly without waiting on a human writer.

📋 Section 3: Define Scoring Criteria

💬 LLM\_EvalCriteriaModel** → Calls GPT-4o-mini again.
📑 Agent\_EvalCriteriaBuilder** → Suggests 5 scoring parameters (scale 1-10).
Example: Clarity, Relevance, Hook Strength, Brand Voice, Scroll-Stoppage.

Benefit: Builds an objective, repeatable evaluation rubric automatically.

🔍 Section 4: Evaluate the Headline

💬 LLM\_HeadlineEvaluatorModel** → Supplies reasoning power.
🔍 Agent\_HeadlineEvaluator** → Applies the 5 criteria to the generated headline and outputs:

JSON with scores per parameter
An average score
A plain-language bottom-line

Benefit: Turns subjective copy quality into measurable numbers.

🔄 Section 5: Decide & Iterate (if needed)

💬 LLM\_BottomLineModel** → Interprets the evaluation results.
🤔 Agent\_IterationDecision** → Decides:

Return NO → headline is acceptable.
Return YES + feedback → headline should be rewritten.
🔀 If\_NeedMoreIterations** → Branches:

If NO → continue workflow.
If YES → (loop wiring possible) headline can be regenerated with feedback.

Benefit: Keeps iterating until the AI headline meets your standards.

📩 Section 6: Deliver the Result

📧 Send a message (Gmail node)** → Sends the accepted headline via email.

Benefit: Automates delivery of the polished, AI-approved headline to your inbox or team.

📊 Workflow Overview

| Section | Purpose | Key Nodes | Benefit |
| -------------------- | ---------------------------------- | ----------------------------------------------------- | ------------------------------ |
| ⚡ Capture Brief | Collect product info & prep prompt | FormTrigger, Set | Structured AI input |
| ✍️ Draft Headline | Generate first headline | LLM\_HeadlineWriterModel, Agent\_HeadlineWriter | Instant creative draft |
| 📋 Define Criteria | Build scoring rubric | LLM\_EvalCriteriaModel, Agent\_EvalCriteriaBuilder | Objective evaluation |
| 🔍 Evaluate Headline | Score headline & summarize | LLM\_HeadlineEvaluatorModel, Agent\_HeadlineEvaluator | Transparent quality check |
| 🔄 Decide & Iterate | Accept or refine headline | LLM\_BottomLineModel, Agent\_IterationDecision, If | Only good results move forward |
| 📩 Deliver Result | Share the final copy | Gmail | Automates delivery |

✅ Final Benefits

🚀 One-click workflow: from product description to tested headline.
📊 Automatic rubric: objective scoring each time.
🔄 Self-improving: poor headlines can auto-iterate with feedback.
📧 Direct integration: approved headlines land in Gmail instantly.
🧩 Fully modular: easy to extend with Google Sheets, Slack, or CRM nodes.