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

✅ 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.