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.

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⚡ 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.

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✍️ 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.

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📋 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.

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🔍 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.

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🔄 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.

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📩 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.

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📊 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

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✅ 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.

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