HTTP 402 AI Tollbooth

The tools are mostly distinct: list_products and preview_product both read product information but are differentiated by catalog search versus curated preview. buy_product could be mistaken for an actual purchase action, but the description clarifies it only returns purchase directions, and list_payment_methods is clearly separate.

All tool names follow a consistent verb_noun snake_case pattern: buy_product, list_payment_methods, list_products, preview_product. The naming is uniform and predictable, even though buy_product's semantics are somewhat misleading.

Four tools is a reasonable count for a narrow tollbooth/payment-oriented server. Each tool has a distinct surface area, though the set is minimal and leans heavily toward read-only operations.

The set covers catalog browsing and payment-method listing, but the only purchase-related tool explicitly never creates an invoice, checkout, or payment. This leaves the core transaction flow incomplete—there is no way to actually complete a purchase or trigger payment, which is likely a significant gap.