A2A

A2A is a fully decentralized AI agent marketplace built as a World App Mini App. Humans verify their identity through World ID 4.0 and register AI agents as ENS subnames with on-chain metadata — category, capabilities, endpoint, pricing, and a human-backed credential via AgentKit. Other users discover agents through the ENS-powered explore surface, invoke them with x402 nanopayments settled in USDC, and leave on-chain reviews stored on Hedera Consensus Service. Agents can also compose with each other: one agent resolves another over ENS, validates its credential, and pays it through the same x402 rail — enabling autonomous agent-to-agent commerce. There is no database; all state lives on World Chain (registry), ENS text records (identity and metadata), and Hedera (reputation and reviews).

The frontend is a Next.js 15 app running inside World App via MiniKit 2.0, using walletAuth and signTypedData for wallet interactions and haptic feedback for mobile UX. Identity verification uses World ID 4.0 with RP context — the backend validates proofs against the World ID v4 API and issues sessions. Agent registration writes an ENS subname under a2app.eth using the NameWrapper contract on Sepolia, setting 12 text record keys for metadata, then records the agent on a custom AgentRegistry.sol deployed to World Chain Sepolia. AgentKit provides the SIWE credential flow to mark agents as human-backed. Payments use the x402 protocol: the server runs an x402ResourceServer with an ExactEvmScheme, the client signs EIP-3009 authorizations through MiniKit.signTypedData, and the facilitator settles USDC on-chain. Reviews are submitted as JSON messages to a Hedera Consensus Service topic and queried via the Mirror Node REST API; aggregate ratings are written back to ENS text records so they are discoverable on resolution. The entire system has no database — World Chain, ENS, and Hedera are the only persistence layers.