Feature request: Storefront MCP server update_cart tool should support line item attributes

MCP & LLM
1

I’m building an AI agent using the Storefront MCP server documented here:

I’m using the update_cart tool, which currently exposes the following parameters:

  • cart_id
  • lines[] with quantity, optional line_item_id, and merchandise_id

Internally, I understand that the Storefront MCP server is using the Storefront GraphQL API, where cart line attributes are supported via mutations like cartLinesUpdate and the CartLineUpdateInput.attributes field:

My use case requires setting line item attributes (for example, engraving text, personalization options, or custom metadata) whenever I add or update items in the cart through the MCP update_cart tool.

Right now, the MCP tool schema for update_cart doesn’t expose an attributes field for each line, so I can’t pass those attributes through MCP even though the underlying Storefront API supports them. The only workaround is to call the Storefront API directly in addition to using the MCP server, which complicates the integration.

Feature request

I’d like to request that the update_cart tool in the Storefront MCP server be extended to support line attributes, for example:

  • In the lines items, add an optional attributes field:
    • attributes: array of { key: string, value: string }

Internally, these could map to CartLineUpdateInput.attributes or the equivalent in the Storefront API.

This would allow AI agents using the Storefront MCP server to:

  • Add personalized items (engraving, custom text, etc.)
  • Attach custom metadata to line items
  • Keep all cart operations going through the MCP tools instead of mixing MCP and direct Storefront API calls

Is this something that could be added to the Storefront MCP server roadmap?
If there is any experimental support or planned API for this, I’d be happy to test and provide feedback.

2

Hi @big_question

Thanks for flagging this - I’m digging into this now to see if this behaviour is a known limitation and to see what would be our recommendation for your use case.

1 Like
3

Hi again @big_question

I can confirm that supporting the setting of line attributes is not currently on the roadmap to support. Your best option right now would be to use the Storefront API separately to make these changes.