WebMCP monitoring for Shopify stores
AI agents shop your store through WebMCP. Know when its tools break.
Shopify turned on WebMCP tools for every Liquid store. MCP Canary opens your store on a schedule, checks the tools agents use, calls a read-only one, and emails you when one breaks or changes.
Free, no signup. Or grade the tool definitions with the WebMCP validator.
$ canary inspect --website https://your-store.com/ https://your-store.com/: PASSED (3.4 s) WebMCP tools registered by the page (document.modelContext). TOOL SIDE EFFECTS search_catalog read_only get_cart read_only search_shop_policies_and_faqs read_only get_ucp_profile read_only # + 8 tools that change the cart or move the page $ canary monitor set my-store \ --website https://your-store.com/ \ --tool search_catalog \ --args '{"catalog":{"query":"gift card"}}' \ --assert '$.products[0].available == true' Created monitor 'my-store'. First check: PASSED▍
Give this to your coding agent
Set up continuous monitoring of the WebMCP tools on our Shopify store with MCP Canary (https://mcpcanary.com/llms.txt), using --website. Choose a read-only tool and a product that always exists, add an assertion on its result, show me the dry run before you enable it, and verify that it works.
What Shopify turned on
WebMCP is a draft browser standard (W3C Web Machine Learning Community Group). A page registers tools in JavaScript with document.modelContext.registerTool(). An agent in the shopper's browser calls them instead of reading the screen and clicking.
Shopify registers WebMCP tools on every Liquid storefront and the Hydrogen developer preview since August 5, 2026, and on eligible checkouts since September 28, 2026. Merchants install nothing, and Shopify documents no opt-out.
The tools act on the shopper's live session: they search your catalog, read products, change the cart, and take the shopper to checkout. When a tool fails, the agent fails on your store, and nothing in your admin shows it.
The docs list 10 tools. Live stores have 12.
On November 4, 2026, two live Liquid stores registered a different tool set than Shopify's WebMCP docs describe. The tools change without a release note on your side, so monitor the real page, not the docs.
| Shopify docs | Live stores |
|---|---|
| update_cart | add_to_cart, update_cart_lines |
| — | get_ucp_profile |
| 8 other tools | the same 8 tools |
What a monitor checks
The page loads
Your store answers, without a bot block, an error status, or a certificate that browsers reject.
The tools register
The page still registers its WebMCP tools. A theme update or an app that breaks the page script shows as WEBMCP_NO_TOOLS.
The contract holds
Each check compares the tool list with the last one: a tool added or removed, an argument added, removed, or changed.
A tool really works
A read-only tool such as search_catalog runs with your arguments, and assertions check the answer, for example that a product is available.
Nothing changes for shoppers
Each check runs in a new, empty browser session that is deleted after it. Tools that change the cart run only if you allow them, and only on that empty cart.
You hear about it
Two failures in a row open an incident and send an email or a signed webhook. One pass resolves it.
Same plans as MCP server monitoring: a 7-day trial with no card, then from $24 a month. See pricing.
Questions
Does my Shopify store have WebMCP tools?
Yes, if it is a Liquid storefront or uses the Hydrogen developer preview. Shopify turned them on for all of these stores. Check your store to see them.
Do I install anything in my store?
No. MCP Canary checks your store from outside, like a shopper's browser. There is no app, no theme change, and no access to your admin.
Will a check change carts or orders?
No. Each check uses a new, empty browser session that is deleted after the check. By default it calls only tools that declare readOnlyHint: true, such as search_catalog.
Can it test the checkout tools?
No. Shopify registers the checkout tools only after proceed_to_checkout with a full cart. A monitor reads one page in one state.
Is it only for Shopify?
No. It works for any web page that registers WebMCP tools with document.modelContext.registerTool(). For MCP servers, see MCP server monitoring.
Who sets it up?
Your coding agent, with the canary CLI: canary monitor set my-store --website URL. Copy the prompt above, or read the docs.
Put a canary in front of your store
Install, then ask your agent to set it up. Or check your store first.
curl -fsSL https://mcpcanary.com/install.sh | sh