Move Shopify agents to UCP Cart MCP before the old Storefront cart tools expire

Shopify has confirmed that Storefront MCP cart tools are being deprecated in favor of UCP Cart MCP. Confidence level: confirmed, with an official changelog and live Shopify documentation. The migration matters for developers building shopping agents because get_cart and update_cart on the old Storefront MCP endpoint remain available only until August 31, 2026.

What changed

Shopify’s June 24, 2026 developer changelog says the cart tools on https://{shop}.myshopify.com/api/mcp are being deprecated. The replacement is Cart MCP at https://{shop-domain}/api/ucp/mcp, implementing the UCP cart capability dev.ucp.shopping.cart version 2026-04-08.

The new Cart MCP exposes four tools: create_cart, get_cart, update_cart, and cancel_cart. Shopify says existing Storefront MCP get_cart and update_cart tools will be maintained until August 31, 2026, but documentation will point to the UCP Cart MCP tools.

Why this is early

This is not an unconfirmed leak. Shopify published the deprecation in its developer changelog and already has Cart MCP documentation live under its agents section.

The early part is adoption. Many commerce agents, demos, and internal tools may still point at the old Storefront MCP endpoint. Teams have a short window to update schemas, agent instructions, endpoint configuration, and retry behavior before the maintained period ends.

Key takeaways

• Shopify is moving cart operations for shopping agents to UCP Cart MCP.
• Old Storefront MCP get_cart and update_cart calls are deprecated.
• Developers should move to https://{shop-domain}/api/ucp/mcp.
• Every request needs a meta object with ucp-agent.profile.
• update_cart replaces the cart’s full state, so partial updates can accidentally remove fields.

Availability and access

Cart MCP documentation is live now. Shopify says Cart MCP accepts unauthenticated requests for create_cart, get_cart, update_cart, and cancel_cart, letting agents estimate totals and share a cart before checkout credentials are collected.

Rate limits still matter. Shopify’s documentation says Cart MCP and Checkout MCP have separate rate limits, with Checkout MCP throttled more strictly. Limits scale based on how the agent identifies itself, and agents should retry using Retry-After with exponential backoff and jitter.

Practical LinkLoot angle

This is a useful migration trigger for anyone building agentic commerce workflows. Check every assistant instruction, MCP client, tool schema, and test fixture that mentions Storefront MCP cart tools. The highest-risk change is update_cart: Shopify documents it as PUT-style replacement, so the agent must send the complete line_items array and relevant context each time.

For broader automation planning, pair this with LinkLoot’s guide to AI workflow automation. Commerce agents need more than product search; they need safe cart state, user confirmation, checkout handoff, rate-limit handling, and rollback behavior.

What to verify before you act

• Search your codebase and agent prompts for https://{shop}.myshopify.com/api/mcp.
• Replace old Storefront MCP cart calls with Cart MCP calls on https://{shop-domain}/api/ucp/mcp.
• Add meta["ucp-agent"].profile to requests and meta["idempotency-key"] for cancel_cart.
• Update tests so update_cart always sends the full desired cart state.
• Confirm your checkout handoff uses Checkout MCP only when the buyer is ready to buy.

Source check

Confirmed by:

• Shopify’s developer changelog entry dated June 24, 2026, which names the deprecated Storefront MCP tools, the UCP Cart MCP replacement, and the August 31, 2026 maintenance date.
• Shopify’s Cart MCP documentation, which documents the endpoint, UCP capability, cart tools, metadata requirements, rate-limit tiers, and PUT-style update behavior.

Early signal / context:

• No community signal is needed for the core claim. This is official Shopify platform documentation with a dated migration notice.