Audit and auto-restructure ad campaigns with Spendict, OpenAI, and Google Sheets

Description

Quick Overview
This workflow collects an ad campaign build brief via an n8n form, audits the structure with Spendict, and automatically rewrites failing builds with OpenAI before re-auditing, then logs the outcome to Google Sheets and posts the verdict to Slack.

How it works
Receives a campaign build brief through an n8n form submission (platform, objective, and free-text campaign structure).
Sends the brief to Spendict’s audit API to score the structure and return a launch recommendation with prioritized fixes.
Routes the flow based on Spendict’s launch recommendation, passing “sound” builds through as-is.
For builds that need changes, sends Spendict’s prioritized fixes to the OpenAI Chat Completions API to generate a revised campaign structure in JSON.
Parses the revised structure and re-audits it with Spendict to produce an updated score and verdict.
Appends the final result (original or auto-restructured) to Google Sheets and posts a summary message to Slack via an incoming webhook.

Setup
Add a Spendict API key via HTTP Header Auth (Authorization: Bearer …) and apply it to both Spendict HTTP requests.
Add an OpenAI API key via HTTP Header Auth (Authorization: Bearer …) for the OpenAI Chat Completions request.
Connect Google Sheets credentials and select the target spreadsheet and sheet in the append step.
Create a Slack Incoming Webhook and replace the placeholder webhook URL in the Slack request.