Storefront MCP tool update_cart failure

[KyleG-Shopify]

Hey everyone, Vedant posted in a separate thread and I was able to identify the issue. See if the solution I provided here will work for you as well:

While creating Cart using update_cart from shopify MCP its giving the checkout url empty

Hey @Vedant_Dere, I’ve dug into this and found the issue. The Storefront MCP documentation is missing some parameter names that the MCP server expects. You followed the docs correctly based on what is there, but the tool you need isn’t in the docs. The example in our documentation shows using a lines array with merchandise_id, but the actual MCP server uses add_items with product_variant_id. You can verify this yourself by calling the tools/list method on your store’s MCP endpoint to see the a…