Catalog summary preview of the 11 agent-runnable service niche briefs (/v1/niches, $0.08): per niche slug, title, target buyer and as_of date. Pass ?category=all|ecommerce|compliance|b2b. Use to pick a slug before calling /v1/niche-brief?slug= ($0.01) or the full 11-brief pack at /v1/niches ($0.08). Ops notes only; no market-size claims. Unknown category returns 404 and is not charged. How to buy: GET the endpoint; it answers HTTP 402 with the exact USDC amount and payTo on Base, then retry with the x402 payment (settles through the Coinbase CDP facilitator). Price is per call.