upsert_theme_file · Shopify Graphql MCP: Risk & Policy

WHAT IT DOES

What upsert_theme_file does on Shopify Graphql

AI agents use upsert_theme_file to create or update resources in Shopify Graphql — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Shopify Graphql environment.

WHY IT NEEDS A POLICY

Why upsert_theme_file needs a policy

This tool creates or modifies theme files in a Shopify store, which are reversible write operations. While high severity due to potential impact on store presentation and customer experience (theme files control storefront HTML/CSS/JS), this is Write rather than Execute because it modifies data/content rather than executing arbitrary code, and Shopify's GraphQL API typically isolates file writes from code execution.

From the tool's definition Tool name 'upsert_theme_file' and description 'Create or update a theme file' directly indicate write operations that create or modify theme files.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

upsert_theme_file Rate-limited

upsert_theme_file stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "upsert_theme_file": {
      "limits": [
        {
          "counter": "upsert_theme_file_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Shopify Graphql, so you can run agents against it safely.

FAQ

Questions about upsert_theme_file

What does the upsert_theme_file tool do? +

Create or update a theme file. It is categorised as a Write tool in the Shopify Graphql MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on upsert_theme_file? +

Register the Shopify Graphql MCP server in PolicyLayer and add a rule for upsert_theme_file: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Shopify Graphql. Nothing to install.

What risk level is upsert_theme_file? +

upsert_theme_file is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit upsert_theme_file? +

Yes. Add a rate_limit block to the upsert_theme_file rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block upsert_theme_file completely? +

Set action: deny in the PolicyLayer policy for upsert_theme_file. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides upsert_theme_file? +

upsert_theme_file is provided by the Shopify Graphql MCP server (uvu-store/shopify-graphql-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.