x402 API market data report. Market report for sellers and builders: for a category (need, e.g. token safety) or the whole x402 index, resource and seller-host counts, hosts with 3+ payers, listed price quartiles, the price where buyers are (payer-weighted median), 30-day calls, estimated 30-day revenue (calls x price, an upper bound), top sellers and the resources with most payers. Use it to price a new endpoint or test a niche for paying demand. limit 1-25 (default 10).