We have a Google Sheet + Google Apps Script workflow that currently drafts eBay listings via the Sell Inventory/Offer APIs (including Gemini-generated descriptions). It works for EBAY_US but we now need to finalize support for EBAY_MOTORS_US, stabilize authentication, and extend the tooling to monitor/respond to buyer messages (via Sell Communication API or 3Dsellers API). Looking for a developer to own the end‑to‑end integration, harden the deployment, and ship documentation. Key Deliverables Marketplace Switch to eBay Motors Ensure all Script Properties (marketplaceId, policy IDs, locations) point to EBAY_MOTORS_US. Validate Motors taxonomy (tree 100) and guarantee all AI-selected categories are valid. Resolve current Sell Offer errors (25005 invalid category, 2004 “Could not serialize marketplaceId”) and confirm multiple SKUs publish successfully. Provide scripts or CLI helpers to wipe/recreate offers for a SKU when marketplace changes. Policy + Location Discovery Tools Enhance the provided fetch_ebay_ids.py (or equivalent) to output Motors-specific fulfillment/payment/return policy IDs and inventory locations using OAuth refresh tokens. Document how to update Script Properties after rotating tokens or policies. OAuth Automation Finalize the existing OAuth CLI (Gemini already wrote scripts/ebay_oauth_cli.js) or improve it so non-technical staff can generate/refresh tokens for both eBay and 3Dsellers. Verify scopes: sell.inventory, sell.account, sell.fulfillment, sell.communication. Messaging Integration Option A: native eBay Sell Communication API (preferred) to fetch buyer messages and post replies. Option B: 3Dsellers public API for messaging (already evaluating their Swagger docs). Implement a pipeline where incoming messages are fetched (via webhook or polling), summarized, and passed to an AI model (Gemini/OpenAI). Provide a review queue UI (Sheet or lightweight web app) before sending responses back through the API. Logging/auditing of AI drafts vs. final replies. AI + Prompt Hardening Refine the Gemini prompts for category/aspect generation so they respect Motors requirements. Add guardrails for AI replies (no off-platform invites, correct tone, shipping disclaimers, etc.). Documentation & Hand-off Step-by-step guide covering environment setup, Script Properties, OAuth/token refresh, category file generation, and message/reply workflow. Suggested monitoring plan (e.g., logs to detect 25005 errors, token expiry alerts). Skills & Experience Google Apps Script (UrlFetch, caching, Script Properties, Sheets custom menus). eBay Sell APIs (Inventory, Offer, Account, Communication) and OAuth 2.0 flows. Familiarity with eBay Motors policies/categories. Optional: 3Dsellers API, Node/Python scripting for tooling, Gemini/OpenAI prompt engineering. Comfortable writing concise documentation and automation helpers. Nice-to-Haves Experience building webhook listeners (Google Apps Script web apps, Cloud Functions, etc.). Prior work on e-commerce automation (Shopify, Amazon, etc.). Knowledge of Gemini or OpenAI integration patterns for customer support. Engagement Details Remote. Start ASAP; initial milestone is restoring Motors publishing (with documentation). Subsequent milestone is the messaging automation + AI responder. If interested, please share: Relevant eBay API/GAS project samples. Estimated timeline for the two milestones. Hourly rate or fixed price for the full scope. Looking forward to partnering with someone who knows the eBay ecosystem inside out!