Assay

Assay is the credit bureau for agent payments on Celo. It reads every x402 settlement on Celo mainnet (858,869 so far) and tests each seller's revenue for what is real: money that goes round in payment loops, and money paid by wallets the seller funded, is struck out. What is left is organic revenue, shown as fineness (organic dollars per 1,000, like 925 sterling) with a rating from AAA to D.

WHAT IT FOUND. Of $194K settled over x402 on Celo, 20% is organic. $125K was paid by wallets the sellers funded themselves, traced to the first transfer that funded each payer; $29K more went round in 9 payment loops, the largest 378 wallets paying each other. 138 of 660 sellers rate D; 8 rate B or better. Of 28,494 ERC-8004 reviews on Celo, 3,438 come from a wallet that ever paid the agent it reviews.

WHO USES IT.

• Agents check a seller before paying: GET /v1/check/:address, $0.002 over x402 (USD₮ default; USA₮, USDC, wARS, wBRL, wCOP accepted, wFIAT gasless through Permit2). Returns pass, caution or block with a signed EIP-712 score. For $0.01, /v1/check/:address/x adds an X search bought on the spot for that buyer through buy.
• withAssayGuard (npm: assayscore) wraps any x402 client so a blocked seller is never paid. assayscore-mcp exposes the same check to any coding or chat agent.
• Sellers buy their signed hallmark ($0.01) and publish it to AssayRegistry from their own wallet; any Celo contract can call isInvestmentGrade(seller). In the browser USA₮ is offered first: verify with Self, claim free USA₮ from the Google Cloud faucet, publish. Scores expire after 7 days, so sellers come back weekly.
• Buyers write payment-verified ERC-8004 reviews carrying the settlement as proofOfPayment.
• Anyone reads any report free at assayscore.xyz.

WHAT X SAYS (buy). Assay buys an X search for every seller's exact address through the buy gateway ($0.005 USDC, x402 from the agent wallet): background under a $0.50 daily cap, busiest and most-asked-about sellers first, weekly; and on demand for agents that pay $0.01 for a fresh one. Posts are evidence, never score. Every payment and its settlement transaction: https://api.assayscore.xyz/v1/paid-calls (reconciled against the chain every 5 minutes).

WHY USA₮. A credit score written to the public record should be paid for in a US-regulated dollar, and USA₮ is the dollar a verified human gets free on Celo, so a seller with no stablecoins can still publish.

ONCHAIN. Agent wallet and x402 PayTo 0x3d5ea1ce6f3Fa5FAe7A38b77F569570b3ea9a9a4; ERC-8004 agent #9981; AssayRegistry 0xf6679308af9ff1ffc11a968dfd1ea5882152e29f (Sourcify verified). Every transaction Assay sends carries the attribution tag; the operator CLI refuses to continue without it. Assay sponsors no gas. Assay never funds user wallets: the CLI refuses to send to any wallet that has paid Assay.

FOR THE ORGANISERS TOO. GET /v1/independent/:address applies the hackathon's own independent-user rule to any PayTo address, free, with reasons per payer and volume inside the window; every report shows the same numbers. Sellers can claim their page by signing one message (name, website, X handle, a badge for READMEs). Agents can buy thirty days of signed rating-change alerts for $0.05 (POST /v1/watch). Celo Agent Visa tiers are shown next to Self proofs. For sellers: a directory at assayscore.xyz/sellers (searchable by name, what they sell and category, with a rating floor; also the MCP tool assay_find_sellers) and, on every report, a plan that says exactly what would raise the rating, computed from the real score formula, which cannot be gamed because funded and looped payers are struck out before scoring. For sellers: a directory at assayscore.xyz/sellers (searchable by name, what they sell and category, with a rating floor; also the MCP tool assay_find_sellers) and, on every report, a plan that says exactly what would raise the rating, computed from the real score formula, which cannot be gamed because funded and looped payers are struck out before scoring.

HONEST NUMBERS. https://assayscore.xyz/stats publishes Assay's usage, revenue (read from Celo), spend on buy, and Assay's own address rated by its own rules. On 21 Oct it rated D: the first paid checks came from a wallet the team funded, and Assay strikes that out like anyone else's. It moves only when wallets Assay never funded pay.

BUILT DURING THE HACKATHON. Scoring engine (loop detection, funding trace, ratings), SQD indexer with RPC failover, API, SDK, MCP server, Solidity registry with Foundry tests, web app. 223 automated tests. Chainstack RPC in production, chosen by a benchmark in the repo.

COUNTERPARTIES. To be named here from the facilitator's settlements to the PayTo address before the deadline.