This MCP server demonstrates moderate quality with a mixed profile. Tool naming follows verb_noun conventions (create-cart, add-to-cart, search-products), which is appropriate. All 6 tools have descriptions present, though most are brief and lack context about when to use them over alternatives. Input schemas are visible and mostly well-formed using Zod validation with type constraints and descriptions. However, several tools have minimal parameter documentation, output schemas are not formally documented in the code, and error handling, while present, lacks the recovery guidance pattern recommended for LLMs. The tools themselves are reasonably composed (separate cart operations vs product operations), but lack some polish around parameter relationships and user-friendly identifier handling. No tool annotations (readOnlyHint, destructiveHint, idempotentHint) are present, which is notable given several tools perform writes (create-cart, add-to-cart, checkout).

• Expand tool descriptions to 100-150 characters each. Follow the pattern: 'WHAT does it do? WHEN should I use it? WHAT does it return?' Example: 'create-cart: Creates a new shopping cart with the specified product (ASIN) and quantity. Use this to start a new purchase session. Returns the cart ID, items summary, and HMAC for subsequent operations.'
• Document output schemas explicitly in tool definitions. Use JSON Schema to describe returned fields, types, and required/optional status. Example for create-cart: returns {cartId: string, items: [{title, price, quantity}], purchaseUrl: string}.
• Add tool annotations: mark create-cart, add-to-cart, checkout with destructiveHint=true (these modify state); mark view-cart, search-products, get-product-details with readOnlyHint=true.
• Enhance error messages with recovery guidance. Instead of 'Failed to create cart', return: 'Failed to create cart: invalid ASIN. Call search-products to find the product ID first, then retry.' Categorize errors: retryable (network), user-fixable (invalid ASIN), fatal (API credentials).
• Document parameter dependencies in descriptions. For add-to-cart, add: 'Requires an active cart created by create-cart. If no cart exists, you will receive an error, use create-cart first.' For checkout, add: 'Use after adding items with create-cart or add-to-cart.'
• Add pagination guidance to search-products description: 'Returns up to [N] results per page. Use the page parameter to iterate results. Each result includes ASIN, pass to get-product-details for full information.'