# Answering agent tool calls

> Whether an agent can call your store's tools for catalog, variant, cart and policy data instead of parsing the rendered page, and whether those calls return correct state under rapid sequential use.

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- **Affects (funnel stage):** Matching
- **Evidence:** spec-fact
- **Confidence:** High (The mechanism is documented first-party, but no engine publishes any link between answering tool calls well and being selected, so the confidence sits below the spec-fact default.)
- **Impact:** 2/3
- **Status:** active
- **Last verified:** 2026-09-18

## Per-platform status

Undocumented platforms show "unknown" - honest unknowns, never invented.

| Platform | Status | Notes | Source |
| --- | --- | --- | --- |
| ChatGPT | partial | ChatGPT calls the merchant's REST checkout endpoints for authoritative cart state. Catalog and variant data arrive through the batch feed, not live tool calls. | [link](https://developers.openai.com/commerce/specs/checkout) (verified 2026-09-18) |
| Gemini / Google AI Mode | partial | Agents discover a store's declared capabilities and endpoints through the UCP manifest and call native or embedded checkout. Per-tool catalog and cart endpoints are not detailed. | [link](https://developers.google.com/merchant/ucp) (verified 2026-09-18) |
| Perplexity | unknown | Not documented by this platform. | - |
| Copilot | unknown | Not documented by this platform. | - |
| Claude | partial | The reference agent reads catalog, variant, cart, order and policy data through structured backend methods rather than parsing pages. This is the deployer's own backend, not a merchant-exposed tool the public Claude discovers. | [link](https://raw.githubusercontent.com/anthropics/commerce-agents/main/shopping-agent/core/shopping_agent/backend.py) (verified 2026-09-02) |

## Evidence and sources

- [WebMCP is live on Liquid storefronts and the Hydrogen developer preview](https://shopify.dev/changelog/webmcp-liquid-hydrogen) (2026-08-05)
- [Storefront MCP cart tools deprecated in favour of UCP Cart MCP](https://shopify.dev/changelog/storefront-mcp-cart-tools-are-being-deprecated-in-favour-of-ucp-cart-mcp) (2026-06-24)
- [Anthropic commerce agents reference implementation](https://github.com/anthropics/commerce-agents) (2026-09-02)

## How to act on this

On Shopify this is largely on by default, so the work is making sure the data behind the tools is right: real stock, a complete variant set, and policies that actually resolve. Elsewhere there is nothing to adopt yet, and the transferable job is the same catalog correctness every other rail reads.

### Handbook chapters
- [Storefronts That Answer Tool Calls, Not Page Reads](https://agentmint.net/handbook/storefronts-that-answer-tool-calls/)

### Related signals
- [UCP profile and order-management readiness](https://agentmint.net/signals/ucp-readiness/)
- [Offer consistency and freshness across surfaces](https://agentmint.net/signals/offer-consistency-freshness/)
- [Machine-readable page representation](https://agentmint.net/signals/machine-readable-mirror/)

## Notes

WebMCP is a proposed standard behind a Chromium origin trial, not a shipped web standard, and the tool surface outside Shopify is thin. Treat this as a direction worth being ready for rather than a lever available on every store today.