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Shopify's old MCP cart tools stop on August 31

The get_cart and update_cart tools on Shopify's Storefront MCP server reached their August 31 deprecation date. Agents that have not moved to the UCP Cart MCP will try to add items to a cart that no longer answers.

Chandni Melwani

Chandni Melwani

Founder & Editor

Aug 31, 2026 · 3 MIN READ

A pair of hands typing on a black keyboard, photographed from directly overhead Photo: Luis Villafranca / Unsplash

The News

Announced June 24, 2026, Shopify is deprecating get_cart and update_cart on https://{shop}.myshopify.com/api/mcp as of August 31, 2026. The replacement is the UCP Cart MCP at https://{shop-domain}/api/ucp/mcp. Shopify's changelog states the tools 'will be maintained until August 31, 2026,' and a Shopify staff member told the developer forum that removal is intended around that date, though he allowed the tools 'may not go away right away.' Merchants running their stores on native Shopify flows are not affected. The only parties who need to act are developers who built custom agents against the old endpoint.

Know More

  • — Deprecated tools: get_cart and update_cart on https://{shop}.myshopify.com/api/mcp, announced June 24, 2026.
  • — Replacement endpoint: https://{shop-domain}/api/ucp/mcp, implementing the UCP cart capability (dev.ucp.shopping.cart, version 2026-04-08).
  • — Breaking change: update_cart uses PUT semantics: each call replaces the cart's full state, so the complete line_items array must be sent every time rather than patching individual fields.
  • — Every request to the UCP Cart MCP must include a meta object carrying ucp-agent.profile. cancel_cart additionally requires a meta idempotency-key (UUID).
  • — Gap: search_shop_policies_and_faqs exists on the old endpoint and has no equivalent on the UCP endpoint as of August 31, 2026. Shopify's changelog deprecates only the cart tools, not that tool.
  • — Also sunsetting, with a caveat: the Checkout Blocks Address Blocker. Shopify's changelog gives the removal date as August 31, 2026; Shopify's own Help Center says it 'will be removed on September 30, 2026.' Two official Shopify sources disagree, so treat neither date as settled. Shopify says compatible rules will be automatically migrated to address format validation.

Shopify gave developers 68 days’ notice. The June 24 changelog entry named August 31 as the date get_cart and update_cart on the old Storefront MCP endpoint would stop being maintained, and August 31, 2026 is that date. A custom agent that has not migrated can still browse the catalogue (product search runs on a separate endpoint that is not part of this deprecation), but the cart step has no fallback. The agent recommends a product, the cart does not update, and the error goes unreported.

A Shopify staff member posting as “Alan_G” put it plainly in the developer forum: “the tool[s] are intended to be removed. They may not go away right away, but it is our intent to remove them around the August 31st deprecation date.” Shopify has not asserted a hard midnight cutoff, and an agent left on the old endpoint may have hours or days before the cart stops responding entirely. The intent is removal; the timing is not fixed.

The new endpoint, https://{shop-domain}/api/ucp/mcp, runs on Universal Commerce Protocol, which Shopify switched on by default for its merchant base on June 17, 2026, and the protocol changes with it. Every request must now carry a meta object with ucp-agent.profile, which is how the UCP capability-negotiation layer identifies the agent. update_cart moves to PUT semantics: the full line_items array must be sent on every call, because the endpoint replaces the cart’s entire state rather than patching it; omit a line item and it disappears. cancel_cart requires a UUID idempotency key. Agents that relied on the old endpoint’s patch-style updates will need their cart-building logic rewritten, not just repointed.

Shopify’s own developer introduction to Catalog, Universal Cart and Checkout Kit, the architecture the cart tools are being retired into. Published August 2025, ten months before the deprecation notice, so it shows where the migration lands and none of the migration itself. Nothing here covers get_cart, update_cart, the meta requirement or the PUT semantics above.

Shopify has not addressed search_shop_policies_and_faqs in this deprecation. The Storefront MCP server documentation still lists it as an active tool on the old endpoint with no deprecation notice, and the June 24 changelog deprecates only the cart tools. There is no UCP equivalent on /api/ucp/mcp. Agents that use the old endpoint to answer shoppers’ questions about shipping, returns and warranties are not being asked to migrate, but they are also not getting a replacement. Whether Shopify will add a UCP equivalent, retire the tool, or leave it in place is not stated in the documentation.

So what: developers who built against the UCP spec have a clean migration; the ones who deferred are now working against an ambiguous deadline. For anyone building a full-service shopping agent, the search_shop_policies_and_faqs gap is the open ground: Shopify has not said how it closes, and cart capability without policy answers is an incomplete integration.

Related

#Shopify#MCP#Agentic Commerce#UCP#Platform Updates#Developer Tools

Frequently Asked Questions

Does this affect merchants who use Shopify's built-in shopping features?

No. Shopify's native commerce flows (its own apps, checkout, and consumer-facing tools) use Shopify's own infrastructure. The August 31 deprecation touches only custom agent integrations built directly against the Storefront MCP endpoint at https://{shop}.myshopify.com/api/mcp. A merchant who has not commissioned or deployed a bespoke AI shopping agent has nothing to do.

What exactly has to change to migrate?

Three things. First, the endpoint URL changes from https://{shop}.myshopify.com/api/mcp to https://{shop-domain}/api/ucp/mcp. Second, every request must now carry a meta object with ucp-agent.profile, a URI identifying the agent's UCP profile. Third, update_cart now uses PUT semantics: the full line_items array must be sent with every call, because the endpoint replaces the cart's entire state rather than patching it. Omitting a line item removes it. cancel_cart also requires a UUID idempotency key in meta.

What happens to search_shop_policies_and_faqs?

That tool is not in Shopify's June 24 deprecation notice, which covers only the cart tools. It remains on the old /api/mcp endpoint and, as of August 31, has no UCP equivalent on /api/ucp/mcp. Whether Shopify will add one, retire the tool, or leave it in place is not stated in their documentation. Agents that rely on it for shipping and returns answers should not assume the old endpoint disappears on the same schedule as the cart tools.

Sources

Chandni Melwani

Chandni Melwani

Chandni Melwani is the founder and editor of New in AI, covering AI agents, M&A, and enterprise adoption. She holds a Master's in Management of Artificial Intelligence from Queen's University and brings a practitioner's perspective from her work in Data and AI leadership.

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