ListingSmith — an open-weight AI listing writer for Etsy & eBay sellers

This is a submission for the Hacktoberfest Open-Source AI Challenge Week 2: Side Hustle

What I Built

ListingSmith turns rough product notes into a sell-ready marketplace listing in seconds. Paste in a few lines about your product — materials, size, story, care instructions — and it produces a marketplace-compliant title, description, bullet points, tags, a price suggestion and an SEO tip, all tuned to the real rules of the platform you picked (Etsy's 140-character titles and 13 tags, eBay's 80-character titles).

It also shows a profit calculator next to every listing: platform listing fees, payment processing, shipping and your margin, in Indian rupees — so a seller knows whether the price actually makes money before they hit publish.

Who would pay for it? Small makers and resellers. Writing one good Etsy listing by hand takes 20–40 minutes of fighting title limits and tag rules. A seller listing 50 products a month gets hours back, and the open-weight models it runs on cost a fraction of a rupee per listing.

Demo

Live demo: https://my-listing-smith.lovable.app

Try it with the sample notes already filled in — pick Etsy or eBay, choose a tone, and hit "Write my listing".

Code

The full source is MIT-licensed:

komalharshita / listing-smith

ListingSmith

Rough notes in, sell-ready listing out. An open-weight AI listing writer for Etsy and eBay sellers, running on DigitalOcean GenAI Serverless Inference.

Built for Hacktoberfest Hack Day Pune × AI Hackers Collective — Best Open-Source AI Project (Side Hustle theme).

Why someone would pay for it

Small makers spend 20–40 minutes per listing fighting title limits, 13-tag rules and SEO. ListingSmith produces a marketplace-compliant title, description, bullets, tags, price check and SEO tip in seconds, for well under a cent per listing.

Why open weights matter here

• Swap models freely — Llama 3.3 70B, Mistral Nemo, DeepSeek R1 Distill, Llama 3 8B. Pick quality vs. speed per listing.
• Cost — open models on serverless inference cost a fraction of closed APIs; a seller can generate hundreds of listings for a few rupees.
• Data control — seller notes go only to the seller's own DigitalOcean endpoint; nothing is stored. Point…

View on GitHub

Highlights of the codebase:

src/lib/listing-pipeline.ts — pure, unit-tested prompt building and output parsing. Marketplace rules (title length, tag count, tag character caps) live here as data, enforced after parsing so the model can never overflow them.
src/lib/listing.functions.ts — the server function that validates input (zod) and routes to either the built-in AI gateway or any OpenAI-compatible endpoint.
src/lib/listing-costs.ts — pure fee/shipping/profit math for Etsy and eBay, with tests.
Dockerfile + .do/app.yaml — one-command deploy to DigitalOcean App Platform.

How I Built It

The stack is TypeScript, React 19, TanStack Start, Tailwind CSS v4 and Vitest, containerised with Docker for DigitalOcean App Platform.

The AI core is built around open-weight models served through DigitalOcean GenAI Serverless Inference (an OpenAI-compatible API). The model picker offers:

Llama 3.3 70B Instruct (Meta)
Mistral Nemo 12B (Apache 2.0)
DeepSeek R1 Distill Llama 70B (MIT)
Llama 3 8B Instruct (fast/cheap tier)

The pipeline is: seller notes → buildMessages() (a system prompt that demands strict JSON with marketplace limits baked in) → model → parseListing() (strips reasoning blocks and code fences, extracts the JSON, then hard-enforces title/tag caps and de-duplicates tags). Because the rules are enforced in code, not just requested in the prompt, the output is compliant even when a smaller model gets sloppy.

Two environment variables configure it: DIGITALOCEAN_GENAI_API_KEY and DIGITALOCEAN_GENAI_BASE_URL.

Why Does Open Innovation Matter?

This project simply doesn't work as a closed-API product:

• Cost — a side-hustle seller can't pay per-token closed-model prices for a tool that saves them 30 minutes. Open-weight models on serverless inference cost well under a cent per listing, so the tool can be free or nearly free
• Data control — sellers' product notes are their business. With an OpenAI-compatible endpoint they choose, notes go only to infrastructure they picked — or nowhere at all, with local Ollama.
• Tunability — the prompt and parsing rules are plain, tested code, and the model is swappable. A seller can fine-tune a Llama on their own best-selling listings and plug it straight in. No closed API offers that without lock-in.
• Licences that match the spirit — the code is MIT, and the models it ships with are Apache 2.0 / MIT / Llama Community License. Anyone can fork it, self-host it, and sell with it.

My Agent Session

I built this with an AI coding agent (Lovable). The agent wrote the pipeline, UI, tests, Dockerfile and deploy spec; I steered the product decisions — the side-hustle angle, the rupee-denominated profit calculator, and the open-weight model lineup.

Prize Categories

Best Open-Source AI Project — the core mechanic is open-weight models (Llama, Mistral, DeepSeek) behind an OpenAI-compatible endpoint, the code is MIT-licensed, and it can run fully offline on local inference.