Search the shelf, or read one item

The catalogue in compact rows — id, name, price in USDC, the price tiers, instant or human-fulfilled, what the item reads, and where to buy it or read its listing. q matches an item's id, name, subtitle and description; max_price_usdc is a ceiling items match at or below; item_id returns that one item with its description and at-a-glance block instead of a list. No filter answers with the whole shelf. Every answer carries what matched and what it matched from, and states that the order is the shelf's own: nothing here is ranked, scored or recommended. A cap that does not parse is a 400 rather than a silently wider answer, and an id the shelf does not carry is a 404 naming the ids it does. Free.