ChatGPT and Codex now call WebMCP tools on your site

OpenAI added WebMCP support to the ChatGPT desktop app's built-in browser on August 25. When ChatGPT Work or Codex lands on a page that exposes WebMCP tools, it can discover and call them instead of guessing at your DOM. If you run a Shopify store, you are already on the supply side of that transaction — Shopify turned WebMCP on for every Liquid storefront three weeks ago.

What actually happened

Per OpenAI's announcement, the feature is called Site tools: a website declares actions an agent can invoke, and the agent uses them on the same live page, inside the shopper's own authenticated session. Update the desktop app and it works on any compatible site. WebMCP is an experimental open standard being developed with Google Chrome, Cloudflare, Shopify, Vercel, Render, and Netlify. OpenAI also opened a build challenge with $35,000 in prizes, submissions due September 3.

The supply side already shipped. Shopify's developer changelog, dated August 5, says WebMCP tools are "live today on every Liquid storefront and on the Hydrogen developer preview" — nothing to install, nothing to configure. The exposed set covers catalog search and product lookup, cart read and update, going to checkout, and policy or FAQ lookup. Agent support is currently limited to Chromium-based browsers through an origin trial.

Why WebMCP matters for your store

You did not opt in, and the tools describe your business. Catalog search returns whatever your product data says. Policy lookup returns whatever your refund page says. An agent reading structured tools will not forgive a variant title that only makes sense to your merchandiser.

The agent runs in the shopper's session. Cart tools call the same storefront actions your apps call. Whatever that logged-in shopper can do, the agent acting for them can do. Treat it as a first-class client, not a scraper.

Test it the way a customer will. Open the ChatGPT desktop browser on your own store and ask it to find a product, add a variant, and read your return window. The gaps you find are copy and data problems, not agent problems.

This is the second interface to your storefront. One is pixels for humans. One is tools for agents. Most stores are shipping the second one unmaintained.

Sources: OpenAI Developer Community, Shopify developer changelog.