How to add an MCP server to your store

It gives an AI agent named actions to run instead of pages to read. MCP, the Model Context Protocol, lets a server "expose tools that can be invoked by language models", and "Each tool is uniquely identified by a name and includes metadata describing its schema", in our words a description of the inputs it accepts. An agent asks for the list with tools/list and runs one with tools/call. For a store, the tools are things like search the catalogue, get a product, add to a basket and start a checkout. Shopify's catalog server, for example, lists search_catalog, lookup_catalog and get_product. A product page is written for people; a tool is a shop assistant that only speaks JSON, which agents happen to like.

Probably, if you are on Shopify or BigCommerce. Choose yours:

On Shopify, the older address went quiet: "The catalog and cart tools on https://{shop}/api/mcp were removed", and the tools now sit on /api/ucp/mcp, where a catalog request must carry the agent's UCP profile. And WooCommerce's server is for running the store rather than for shoppers. Its default server "requires an authenticated user with the read capability", signed in with a WordPress Application Password, and its abilities create and update products and read orders. Handing that to a shopper's agent would be handing over the stockroom keys. The Shopify, WooCommerce, BigCommerce and Magento guides cover the rest of each platform.

Start from the transport. MCP's versioning page says "The current protocol version is 2026-07-28", and in that revision "The server MUST provide a single HTTP endpoint path (hereafter referred to as the MCP endpoint) that supports POST." The revision removed "the GET stream endpoint" and "protocol-level sessions", so every call stands alone. Each request carries its protocol version twice, in an MCP-Protocol-Version header and in the body's _meta, plus an Mcp-Method header that repeats the method, and for tools/call an Mcp-Name header that repeats the tool name. The client "MUST include an Accept header listing both application/json and text/event-stream".

Build a request below and copy it as a curl command. Point it at your server once it is running, or at a platform's, to see what comes back.

curl -X POST 'https://shop.example.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H 'MCP-Protocol-Version: 2026-07-28' \
  -H 'Mcp-Method: tools/list' \
  --data '{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list",
  "params": {
    "_meta": {
      "io.modelcontextprotocol/protocolVersion": "2026-07-28",
      "io.modelcontextprotocol/clientInfo": {
        "name": "ExampleClient",
        "version": "1.0.0"
      },
      "io.modelcontextprotocol/clientCapabilities": {}
    }
  }
}'

The spec also fixes how a server answers a wrong request. If the header and the body disagree, the server "MUST reject the request with 400 Bad Request and a HeaderMismatch JSON-RPC error". A method it does not implement gets "404 Not Found and a JSON-RPC error with code -32601". If you build on an MCP SDK, check that it supports the 2026-07-28 revision before you rely on it for these.

If you sell through UCP, the ones UCP defines. UCP's MCP binding for release 2026-08-25 names 13 methods, from create_checkout to get_product, which our check groups by capability (checkout, cart, catalog search, catalog lookup and order) from their names. List the tools for each capability your UCP profile declares. The planner shows what our MCP check expects and how it grades a list that is short a few.

A few rules from MCP's tools page shape the details:

• Names: "Tool names SHOULD be between 1 and 128 characters in length (inclusive)", using letters, digits, underscore, hyphen and dot.
• Baskets: MCP has no sessions, so a server that keeps a shopping cart across calls "should do so by returning an explicit handle", an ID the agent passes back each time. Without sign-in, the handle "should be generated with sufficient entropy (e.g., a UUIDv4) and given a bounded lifetime", and the tool description should say how long, for example "baskets expire after 24 hours of inactivity".
• Who sees what: the tool list "MAY vary by the authorization presented on the request", so a signed-in agent can see order tools that a guest does not.

MCP's tools page says servers "MUST: Validate all tool inputs · Implement proper access controls · Rate limit tool invocations · Sanitize tool outputs". The transport page adds that servers "MUST validate the Origin header on all incoming connections to prevent DNS rebinding attacks" and answer an invalid one with "HTTP 403 Forbidden", and that they "SHOULD implement proper authentication for all connections". MCP itself says "Authorization is OPTIONAL for MCP implementations"; where an HTTP server does use it, "MCP servers MUST implement OAuth 2.0 Protected Resource Metadata", which why agents stall at checkout explains.

In practice, for a store, we would add our own rules. Keep payment out of the server and hand the buyer a checkout link instead, the way Shopify's Checkout MCP does with its continue_url. Do not put secrets or personal data in x-mcp-header parameters: MCP says sensitive parameters "SHOULD NOT" be marked that way, "as header values are visible to network intermediaries". And keep a catalogue tool from returning anything your public product page does not show. The bot protection guide covers telling a well-behaved agent from a scraper at the door.

Two ways, and you can use both. A UCP agent reads your profile at /.well-known/ucp, where a service entry with "transport": "mcp" and an endpoint gives the address. A generic MCP client looks for a server card. Cards come from SEP-2127, marked "Final" on MCP's site, which says "Cards themselves can be hosted at any unreserved URI, with /server-card reserved as the recommended location". The extension's own repository still opens with "Status: Experimental", so the two labels disagree for now. Build a card here:

{
  "$schema": "https://static.modelcontextprotocol.io/schemas/v1/server-card.schema.json",
  "name": "com.example/shop",
  "version": "1.0.0",
  "description": "Search Northwind Linen’s catalogue and build a basket.",
  "remotes": [
    {
      "type": "streamable-http",
      "url": "https://shop.example.com/mcp",
      "supportedProtocolVersions": [
        "2026-07-28"
      ]
    }
  ]
}

A card is public by design: "servers MUST NOT include credentials, internal network topology, proprietary logic, or user/session-specific data", and "Wide-open CORS (Access-Control-Allow-Origin: *) is acceptable". It describes the server and leaves out the tools, which an agent asks the server for. Cards are "optional and additive", so a server without one still works for a client that already has its address.

TRX-013 asks your MCP server for its tools once per scan, with one tools/list POST in the 2026-07-28 form shown above, and only when your UCP profile declares an MCP endpoint. It passes a list that has every tool UCP defines for your declared capabilities, and grades a shorter list by the share it has, never below 40. A JSON-RPC error warns, a 404 or an answer that is not JSON-RPC fails, and a refusal (401, 403, 429), a server error or a redirect makes it skip. DISC-012 looks for a server card. DISC-007 looks for agent commerce discovery documents, your UCP profile among them.

Our checks have gaps of their own:

• DISC-012 looks for the card at /.well-known/mcp/server-card.json, then /.well-known/mcp.json, which are older draft paths, and not at SEP-2127's <streamable-http-url>/server-card. When it finds no card but your UCP profile declares an MCP server, it warns rather than fails. Until our check catches up, a copy of the card at the first path keeps both readers happy.
• DISC-007 still counts a 405 or 400 answer at Shopify's older /api/mcp address as an MCP endpoint, though Shopify says the catalog and cart tools there were removed.
• TRX-013 reads tool names only. Whether a tool works when called is beyond a check that sends one request and never buys anything.

Do I need an MCP server to sell through AI agents?

No. Agents can read your product pages and use your checkout like a visitor. An MCP server gives them tools instead, and on Shopify and BigCommerce the platform provides it. See the agent readiness checklist for where it sits among the other tasks.

What is the current MCP version?

2026-07-28. MCP's versioning page says "The current protocol version is 2026-07-28".

Where is Shopify's MCP endpoint?

At https://{shop}/api/ucp/mcp. Shopify says "UCP now provides these capabilities at https://{shop}/api/ucp/mcp" and that the catalog and cart tools on /api/mcp were removed.

Is WooCommerce's MCP for shoppers' agents?

Not as documented. WooCommerce says its MCP "is currently in developer preview", and its default server "requires an authenticated user with the read capability". It is a way for you and your tools to manage the store.

Where should I publish an MCP server card?

SEP-2127 recommends <streamable-http-url>/server-card, the MCP address with /server-card added. Our DISC-012 reads /.well-known/mcp/server-card.json and /.well-known/mcp.json today, so serving the same card at the first of those as well covers both.

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