WebMCP Commerce Tools

Before writing code

Fetch live docs:

1. Fetch https://developer.chrome.com/blog/webmcp for commerce-related examples and guidance
2. Web-search webmcp agentic commerce e-commerce tools examples for community implementations
3. Web-search webmcp shopping agent checkout cart tools for commerce workflow patterns
4. Web-search site:github.com webmcp commerce for open-source commerce tool implementations

Conceptual Architecture

Agentic Shopping Flow

A typical agent-driven shopping session using WebMCP:

User: "Find me wireless headphones under $100"
  → Agent navigates to retailer site
  → Site registers tools: [searchProducts, viewDetails, addToCart, checkout]
  → Agent calls searchProducts(query="wireless headphones", maxPrice=100)
  → Site returns structured product list
  → Agent presents results to user
  → User: "Add the Sony ones to my cart"
  → Agent calls addToCart(productId="sony-wh-1000", quantity=1)
  → Agent: "Added! Proceed to checkout?"
  → User: "Yes, use my saved card"
  → Agent calls checkout(useSavedPayment=true)
  → Site: requestUserInteraction → User confirms → Order placed
  → Agent: "Order #1234 confirmed!"

Core Commerce Tool Set

Every e-commerce site should consider these tool categories:

1. Product Discovery

• searchProducts(query, filters) — Catalog search with optional filters
• getCategories() — List product categories
• viewProductDetails(productId) — Full product info, images, reviews
• compareProducts(productIds) — Side-by-side comparison

2. Cart Management

• addToCart(productId, quantity, variant) — Add item to cart
• removeFromCart(itemId) — Remove item from cart
• updateCartQuantity(itemId, quantity) — Change quantity
• getCartContents() — View current cart
• applyCoupon(code) — Apply a discount code

3. Checkout

• getShippingOptions(address) — Available shipping methods and costs
• checkout(paymentMethod, shippingOption) — Complete purchase
• getOrderSummary() — Pre-checkout order review

4. Order Management

• getOrderHistory(filters) — Past orders with optional date/status filters
• getOrderStatus(orderId) — Track a specific order
• initiateReturn(orderId, items, reason) — Start a return
• cancelOrder(orderId) — Cancel a pending order

5. Account & Subscriptions

• manageSubscription(action, planId) — Upgrade, downgrade, cancel subscriptions
• getSubscriptionDetails() — Current subscription info
• updateShippingAddress(address) — Update default address

6. Support

• createSupportTicket(type, description) — Open a support case
• checkTicketStatus(ticketId) — Check on existing ticket

Tool Design Principles for Commerce

1. Mirror existing APIs — Tool execute callbacks should call your existing REST/GraphQL APIs
2. Reuse session — Tools run in the user's authenticated browser session; no extra auth needed
3. Structured returns — Return JSON with consistent structure (items array, totals, status)
4. Progressive disclosure — Start with search and browse tools; add checkout only for authenticated users
5. Confirmation gates — Require user interaction for anything involving money

Multi-Site Agent Workflows

Agents can navigate across multiple retailer sites:

1. Search on Site A using WebMCP → get results
2. Search on Site B using WebMCP → get results
3. Compare across sites at the agent level
4. Purchase from the best option using that site's checkout tool

Each site maintains its own tools; the agent coordinates across them.

Integration with Backend Protocols

WebMCP tools can delegate to backend protocols:

• UCP endpoint — searchProducts tool calls a UCP product discovery API
• Stripe Checkout — checkout tool creates a Stripe session server-side
• Inventory service — Tools check real-time stock via internal APIs

Best Practices

• Expose tools progressively: read-only tools for all visitors, transactional tools for logged-in users
• Return pagination info for list results (total, page, hasMore)
• Include product images/thumbnails in results as URLs (agents can display them)
• Handle out-of-stock gracefully — return clear status, not errors
• Test the full purchase flow with an AI agent end-to-end
• Consider mobile/responsive — tools should work regardless of viewport

Fetch the latest WebMCP examples and commerce community patterns before building your tool set.