Agentic Commerce (ChatGPT Instant Checkout) is a real step forward for product discovery. But once you look closer at what you give up - the tradeoffs are significant.
OpenAI takes 4% on every transaction through Instant Checkout. Your brand voice gets replaced by a generic AI tone. Customer conversation data flows through OpenAI's infrastructure. And you have zero visibility into what's actually driving conversions.
If you've already built your commerce stack on MedusaJS to stay in control - handing that control to a third-party AI integration defeats the point.
We built a custom ChatGPT App SDK that connects directly to your Medusa backend. Full shopping experience inside ChatGPT, without giving up the things your team worked to own: brand identity, customer data, and margin.
What's Inside
Branded ChatGPT Application
Your store gets its own ChatGPT App - custom name, custom icon, custom behavior. Users tag your store in ChatGPT and get a shopping experience that reflects your brand, not a generic assistant.
Custom System Prompts
Define exactly how the AI represents your brand: tone of voice, product priorities, upsell rules, competitor handling, language constraints. Updated anytime without code changes
MCP UI Components
Interactive product cards rendered right inside the chat - image carousels, variant selectors, color swatches, size guides, cart widgets. Built as React components with full creative freedom, connected to your Medusa product data
Full Cart & Checkout Flow
Not single-item redirects. A complete cart experience inside the conversation - add multiple items, apply discount codes, proceed to your native Medusa checkout with full session continuity.
Storefront Widget Embedding
The same ChatGPT App embeds as a first-party chat widget on your storefront. One AI brain, two touchpoints. Cart and session sync seamlessly between chat and storefront.
Conversion Attribution
Track the full funnel: what customers asked, what the AI recommended, what was viewed, added to cart, and purchased. Feed it directly into your existing analytics stack.
Who This Is Built For
Headless Teams Paying the Commission Tax
You chose MedusaJS to avoid platform fees and vendor lock-in. A custom ChatGPT App keeps checkout on your own store - same AI discovery channel, zero commission to OpenAI.
Teams with Custom Commerce Workflows
Your Medusa setup has custom modules, non-standard checkout logic, or complex product structures. Your ChatGPT App should reflect that - not force you into a generic integration
Brands Losing Their Voice
Generic AI presents your product the same way it presents a budget alternative. A custom system prompt puts your brand team back in control of every customer conversation
What ChatGPT Native Takes — What We Give Back
4% commission on every sale
0%. Checkout stays on your Medusa store
Generic AI tone, no brand voice
Fully customizable system prompts per merchant
No access to conversation or conversion data
Full funnel visibility - queries, views, cart, purchase
Customer data shared with OpenAI
100% first-party data, stays within your stack
Limited product cards, single-item checkout
Rich MCP UI components — carousels, swatches, full cart
GDPR/CCPA exposure from third-party data flow
Compliant by design - data never leaves your backend
No storefront presence — ChatGPT only
Same assistant embeds as a widget on your own site
Up and Running in a Day
Install the SDK in a new Next.js project
Connect your store via MCP server
Write your system prompt - brand voice, tone, product rules
Customize UI components to match your brand
Register your ChatGPT App with OpenAI
Optionally embed as a widget on your storefront
Deploy - your ChatGPT App goes live
Built for MedusaJS
Works Where You Already Sell
Custom ChatGPT App live on open-source headless commerce too
OpenAI API costs run roughly $0.01–0.03 per conversation, billed directly to your OpenAI account. Even at low conversion rates, the per-conversion AI cost is well under $1 - versus $4 on a $100 order at 4% commission. The economics aren't close
The full commerce flow - product browsing, cart management, and order placement, all inside ChatGPT. We've built and demoed this end-to-end. Product cards render from your live Medusa catalog, cart operations run against the Medusa API, and completed orders appear in your Medusa admin dashboard immediately.
The integration is built on Medusa's REST API and is compatible with both Medusa v1 and v2. Custom modules and non-standard configurations are supported — we review your setup during onboarding.
The backend is framework-agnostic. The storefront widget works with Next.js, Remix, Hydrogen, or vanilla JavaScript. The core MCP server and AI orchestration layer have no frontend dependency
Conversation data stays within your infrastructure. The MCP server connects the AI to your Medusa backend without routing customer data through OpenAI's generic pipeline. Your data stays first-party - relevant for GDPR and CCPA compliance.
