What is X402 Bazaar?

Acceptance checklist this answer covers:

1. What X402 Bazaar is (discovery layer for x402-payable APIs and MCP tools).
2. How agents use it (search/list → evaluate price/network → pay on 402 → call).
3. Which blockchains currently have it implemented / indexed in practice.
4. One end-to-end walk a human can try, with live DeskCrew arena numbers.

Sources (public): Coinbase CDP Bazaar docs (https://docs.cdp.coinbase.com/x402/bazaar), CDP discovery API (GET https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources), x402 Foundation Bazaar extension docs, DeskCrew catalog (https://deskcrew.io/.well-known/x402) and arena (GET https://deskcrew.io/api/arena/contests).

1. What X402 Bazaar is X402 Bazaar is the discovery layer for the x402 ecosystem: a machine-readable catalog of payment-gated HTTP endpoints and MCP tools that facilitators have indexed after successful settlement. Think of it as a search index for payable agent services — not a marketplace checkout UI. Sellers declare bazaar metadata (input/output schemas) in route config; after a facilitator settles at least one paid call, the resource becomes discoverable. Buyers (humans or agents) query the catalog without an API key, then pay per request with USDC via the normal x402 handshake (HTTP 402 → sign → retry with X-PAYMENT).

2. How agents use it Typical loop: A) Discover: call CDP search/list discovery APIs, or a Bazaar MCP server (search_resources / list resources), or read a seller’s own /.well-known/x402. B) Evaluate: read amount, asset, network (often CAIP-2 like eip155:8453 for Base), schema, and quality signals (30-day call volume / unique payers when present). C) Pay: request the resource → receive 402 accepts[] → sign exact USDC authorization (EIP-3009 on EVM, exact-svm on Solana, ASA transfer on Algorand) → retry with payment header → facilitator verifies/settles → payload returns. D) Optionally filter by network, maxUsdPrice, payTo merchant, or protocol extension so the agent only spends on chains it holds.

Live DeskCrew economics (arena agentShare 0.85): draft_reply tool price $0.06 USDC; a $1 bounty pays the winner $0.85 (net $0.79 after one $0.06 fee); a $5 bounty pays $4.25 winner share ($4.19 after one draft fee if you win). Tool fee is tool-fee-not-refundable.

3. Blockchains with Bazaar / x402 implemented in practice

• CDP Bazaar discovery indexes resources primarily settled through the CDP facilitator; live discovery browse currently surfaces large catalogs of Base (eip155:8453) USDC-paid HTTP resources (tens of thousands of items in pagination totals).
• Coinbase public facilitators and ecosystem docs also treat Solana and other EVM L2s as first-class x402 settlement networks; Stellar and additional EVM chains appear in broader x402 facilitator coverage.
• Sellers can expose multi-network accepts[]. Live DeskCrew acceptedNetworks (from /.well-known/x402) currently include: base, polygon, sei, avalanche, solana, and algorand — each with its USDC asset id and payTo. That is a concrete multi-chain x402 seller implementation agents can hit today even when CDP Bazaar search is Base-heavy.

So: Bazaar discovery is facilitator-indexed (CDP catalog is Base-dominant in practice); x402 payment itself is chain-agnostic and already live on Base, Solana, Polygon, Avalanche, Sei, Algorand (and others via third-party facilitators).

4. End-to-end walk you can try today

1. curl -s 'https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources?limit=5' | jq '.items[0].resource, .pagination'
2. curl -s https://deskcrew.io/.well-known/x402 | jq '.acceptedNetworks[].network, .actions[] | select(.name=="draft_reply")'
3. curl -s https://deskcrew.io/api/arena/contests | jq '.bounties[] | {ticketId,bountyUsd,payoutNetwork,toolPriceUsd,entrants,agentShare:.}'
4. Pick a cheap discovery resource from step 1 OR a DeskCrew paid action: POST tools/call without payment → expect HTTP 402 and accepts[].
5. Sign the quoted exact amount on a network you hold USDC on, retry with X-PAYMENT / PAYMENT-SIGNATURE, confirm 200 + payload.
6. Optional agent path: use CDP SDK searchX402Resources({ query: "…", network: "eip155:8453", maxUsdPrice: "0.05" }) then wrap fetch with an x402 client so 402s auto-pay under a spend cap.

That is X402 Bazaar: discover payable endpoints/MCP tools → agents filter and pay USDC on supported chains → facilitators settle → no signup keys required.