Add a product to cart on any UCP-enabled Shopify store and get a checkout URL. Requires a variant ID from the search-catalog or get-product-details results. Returns the cart contents, checkout URL, and a cart_id token. To build multi-item carts: pass the returned cart_id back on subsequent calls....
Part of the UCP Checker server.
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AI agents use add-to-cart to create or modify resources in UCP Checker. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call add-to-cart repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach UCP Checker.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"add-to-cart": {
"limits": [
{
"counter": "add-to-cart_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full UCP Checker policy for all 10 tools.
These attack patterns abuse exactly the kind of access add-to-cart gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Add a product to cart on any UCP-enabled Shopify store and get a checkout URL. Requires a variant ID from the search-catalog or get-product-details results. Returns the cart contents, checkout URL, and a cart_id token. To build multi-item carts: pass the returned cart_id back on subsequent calls. The agent holds the cart_id — no server-side session needed. Example: domain: "allbirds.com", variantId: "gid://shopify/ProductVariant/12345" Multi-item: domain: "allbirds.com", variantId: "...", cartId: "gid://shopify/Cart/abc123". It is categorised as a Write tool in the UCP Checker MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the UCP Checker MCP server in PolicyLayer and add a rule for add-to-cart: 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 UCP Checker. Nothing to install.
add-to-cart is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the add-to-cart 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.
Set action: deny in the PolicyLayer policy for add-to-cart. 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.
add-to-cart is provided by the UCP Checker MCP server (ucpchecker/ucp-checker). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 10 UCP Checker tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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