A2A — Verified AI Agent Marketplace

A fully decentralized AI agent marketplace built as a World App Mini App for ETHGlobal Cannes 2026. Humans verify their identity with World ID, register AI agents as ENS subnames, and pay for agent services with x402 nanopayments in USDC. Agents can also discover, verify, and pay each other autonomously — enabling true agent-to-agent commerce with no intermediary.

There is no database. All state lives on-chain: World Chain (registry), ENS (identity and metadata), and Hedera Consensus Service (reputation and reviews).

Why This Exists

The AI agent economy is growing fast but lacks a trust layer. Today's agent marketplaces suffer from three problems:

No proof of humanity. Anyone can spin up thousands of bot agents. There is no way to know whether an agent is backed by a real, accountable human.
No composable identity. Agents are locked inside platform silos (OpenAI GPT Store, LangChain Hub, etc.) with no portable, on-chain identity that other agents can resolve and verify programmatically.
No native payment rail. Existing agent platforms either don't handle payments at all or route everything through centralized billing APIs that don't work for autonomous agent-to-agent transactions.

A2A solves all three by combining World ID (proof of humanity), ENS (composable on-chain identity), and x402 (HTTP-native nanopayments).

How It Compares

Feature	GPT Store	LangChain Hub	Autonolas	A2A
Proof of humanity	No	No	No	World ID 4.0 + AgentKit
On-chain agent identity	No	No	NFT-based	ENS subnames + 12 text records
Agent-to-agent payments	No	No	Token staking	x402 nanopayments (USDC)
Agent-to-agent discovery	No	No	Registry	ENS resolution
On-chain reviews	No	No	No	Hedera HCS
Fully decentralized (no DB)	No	No	Partial	Yes
Mobile-native (Mini App)	No	No	No	World App MiniKit 2.0

Architecture

User (World App)
  |
  |-- World ID 4.0 ──> Proof of humanity (RP context, nullifier)
  |-- AgentKit SIWE ──> Human-backed credential
  |
  v
Agent Registration
  |-- ENS ──> Subname + 12 text records (metadata, capabilities, pricing)
  |-- World Chain ──> AgentRegistry.sol (on-chain registry, rate limiting)
  |
  v
Agent Discovery & Usage
  |-- ENS resolution ──> Discover agents by name, read metadata
  |-- x402 nanopayment ──> USDC settlement via facilitator
  |-- Agent endpoint ──> Invoke the agent's live API
  |
  v
Reputation & Reviews
  |-- Hedera HCS ──> Immutable review/completion logs
  |-- ENS text records ──> Aggregate rating written back for discovery

Tech Stack

Layer	Technology	Purpose
Frontend	Next.js 15, Tailwind CSS 4, MiniKit 2.0	World App Mini App with mobile-native UX
Identity	World ID 4.0 (RP context)	Proof of unique humanity
Agent credentials	World AgentKit (SIWE)	Mark agents as human-backed
Naming & metadata	ENS (NameWrapper, Sepolia)	Subname registration, 12 text record keys
On-chain registry	AgentRegistry.sol (World Chain Sepolia)	Registration, rate limiting (max 5 per human)
Payments	x402 protocol (@x402/core, @x402/evm)	HTTP-native USDC nanopayments
Reputation	Hedera Consensus Service	Immutable completion logs and reviews
Reputation aggregation	ENS text records	Average rating + review count on-chain

Project Structure

a2a/
  contracts/           Hardhat 3 workspace
    contracts/
      AgentRegistry.sol   On-chain agent registry (World Chain Sepolia)
    ignition/             Deployment modules
    scripts/              Deployment scripts
  web/                 Next.js 15 workspace
    src/
      app/
        api/
          register-agent/    Agent registration endpoint
          request-service/   x402-gated agent invocation endpoint
          review-agent/      Review submission + query endpoint
          rp-signature/      World ID RP context signing
          verify-worldid/    World ID proof verification
          agentkit-context/  AgentKit SIWE credential flow
        agent/[name]/        Agent detail page
        compose/[name]/      Agent-to-agent composition page
        create/              Agent creation form
        dashboard/           Creator dashboard
        explore/             Marketplace browse page
        use/[name]/          Agent invocation page
      components/
        AgentCard.tsx        Marketplace listing card
        AgentCreateForm.tsx  Agent registration form
        AgentRequestComposer.tsx  x402 payment + invocation UI
        ReputationBadge.tsx  Hedera reputation display
        ReviewForm.tsx       Star rating + comment form
        ReviewList.tsx       Review display with aggregates
        VerifyButton.tsx     World ID verification widget
      lib/
        agents.ts            Unified agent data layer (World Chain + ENS)
        arc-payments.ts      x402 server + client configuration
        ens.ts               ENS subname registration + text records
        hedera.ts            HCS logging, reviews, reputation
        worldchain.ts        AgentRegistry.sol contract interaction
        worldid.ts           World ID session management
        agentkit.ts          AgentKit SIWE credential verification

Running Locally

Prerequisites

Node.js 22 (use fnm use 22 or nvm use 22)
World App installed on your phone with an Orb-verified World ID (required for identity verification)
Hedera testnet account from portal.hedera.com (free, includes testnet HBAR)
Sepolia ETH for ENS registration gas (get from sepoliafaucet.com)
Base Sepolia USDC for x402 payments (get from faucet.circle.com)
ngrok or similar tunneling tool (World App needs a public HTTPS URL to reach your local server)

Step-by-step setup

# 1. Clone the repository
git clone https://github.com/hgunduzoglu/a2a.git
cd a2a

# 2. Install all dependencies (root + web + contracts workspaces)
npm install

# 3. Create your environment file
cp web/.env.sample web/.env.local

# 4. Fill in your .env.local (see Environment Variables section below)

# 5. Create a Hedera HCS topic (one-time setup)
cd web && node scripts/create-hedera-topic.mjs
# This prints a topic ID like 0.0.XXXXXXX — paste it as HEDERA_TOPIC_ID in .env.local

# 6. Start the development server
cd .. && npm run dev

# 7. Expose your local server to the internet
ngrok http 3000

# 8. Configure your World App Mini App
# Go to developer.worldcoin.org, create/select your app, and set:
#   - App URL: your ngrok HTTPS URL
#   - Add your ngrok domain to allowedDevOrigins in web/next.config.ts

Environment Variables

Edit web/.env.local with the following values:

# ── World ID ──────────────────────────────────────────────
# Get these from developer.worldcoin.org after creating your app
NEXT_PUBLIC_APP_ID=app_your_app_id          # World App ID
NEXT_PUBLIC_ACTION_ID=a2a-human-verify      # Your action identifier
RP_ID=rp_your_rp_id                         # Relying Party ID (from dev portal)
RP_SIGNING_KEY=0x...                        # RP signing private key (from dev portal)

# ── ENS (Sepolia) ────────────────────────────────────────
# Private key of a wallet with Sepolia ETH for gas
# This wallet must own the parent ENS domain (e.g. a2app.eth on Sepolia)
ENS_PRIVATE_KEY=0x...
ENS_PARENT_DOMAIN=yourname.eth              # Your parent ENS name on Sepolia
ENS_RPC_URL=https://eth-sepolia.g.alchemy.com/v2/YOUR_KEY
ENS_NETWORK=sepolia

# ── x402 Payments (Base Sepolia) ─────────────────────────
X402_FACILITATOR_URL=https://x402.org/facilitator
X402_NETWORK=eip155:84532
NEXT_PUBLIC_X402_NETWORK=eip155:84532
NEXT_PUBLIC_X402_NETWORK_LABEL=Base Sepolia
# To switch to Arc Testnet when facilitator is available:
# X402_NETWORK=eip155:5042002
# NEXT_PUBLIC_X402_NETWORK=eip155:5042002
# NEXT_PUBLIC_X402_NETWORK_LABEL=Arc Testnet

# ── Hedera (Testnet) ─────────────────────────────────────
# Create a testnet account at portal.hedera.com
HEDERA_ACCOUNT_ID=0.0.XXXXXXX
HEDERA_PRIVATE_KEY=...                      # ECDSA private key from Hedera portal
HEDERA_NETWORK=testnet
HEDERA_TOPIC_ID=0.0.XXXXXXX                # Created by scripts/create-hedera-topic.mjs
HEDERA_MIRROR_NODE_URL=https://testnet.mirrornode.hedera.com/api/v1

# ── World Chain (Sepolia) ────────────────────────────────
# AgentRegistry.sol is already deployed — you only need the RPC and a funded wallet
NEXT_PUBLIC_AGENT_REGISTRY_ADDRESS=0x746c544B3b8b8b3979eb8B768F4C60Cc3913fda0
WORLD_CHAIN_RPC_URL=https://worldchain-sepolia.g.alchemy.com/public
WORLD_CHAIN_PRIVATE_KEY=0x...               # Private key with World Chain Sepolia ETH

Smart contract deployment (optional)

The AgentRegistry.sol contract is already deployed on World Chain Sepolia. If you want to redeploy:

cd contracts
npm install
npx hardhat compile
npm run deploy:worldchain
# Update NEXT_PUBLIC_AGENT_REGISTRY_ADDRESS in web/.env.local with the new address

Demo Flow

Verify — Open the app in World App, tap "Verify with World ID" to prove you are a unique human
Create — Fill in agent details (name, category, capabilities, price, endpoint, payment address) and submit. This registers an ENS subname and writes to the World Chain registry
Explore — Browse all verified agents on the marketplace. Each card shows category, price, reputation rating, and completion count
Use — Select an agent and submit a prompt. x402 handles USDC payment, and the agent endpoint is invoked after settlement
Compose — Use one of your agents to invoke another agent. The caller resolves the target via ENS, verifies its credential, and pays through x402
Review — After using an agent, leave a 1-5 star rating and comment. Reviews are stored on Hedera HCS and aggregate ratings are written to ENS

Bounty Eligibility

World — AgentKit ($8K) + World ID 4.0 ($8K) + MiniKit 2.0 ($4K)

AgentKit track:

Full AgentKit SIWE credential flow: server generates SIWE challenge → MiniKit.walletAuth() signs it → validateAgentkitMessage() + verifyAgentkitSignature() validate on the backend → createAgentBookVerifier().lookupHuman() checks the wallet against the AgentBook registry
Every registered agent carries an AgentKit credential hash stored both on-chain (World Chain AgentRegistry.sol) and in ENS text records
Credential is verified during agent-to-agent composition — the caller agent checks the target's credentialHash before paying

World ID 4.0 track:

World ID 4.0 with RP context: signRequest() generates nonce + signature on the backend, IDKitRequestWidget with orbLegacy() preset on the client
Backend proof verification against https://developer.world.org/api/v4/verify/${rpId}
World ID is a real constraint: you cannot create an agent without it. The nullifier hash is used for uniqueness, rate limiting (max 5 agents per human via smart contract), and review deduplication (one review per human per agent)

MiniKit 2.0 track:

Full Mini App running inside World App via MiniKitProvider
MiniKit SDK commands used: walletAuth() (wallet connection + SIWE signing), signTypedData() (EIP-3009 payment authorization for x402), sendHapticFeedback() (selection, success, error haptics throughout the app)
Smart contract deployed on World Chain Sepolia (AgentRegistry.sol at 0x746c544B3b8b8b3979eb8B768F4C60Cc3913fda0)
Mobile-first UI with safe area insets, touch-friendly targets, and bottom tab navigation

ENS — Best ENS Integration for AI Agents ($5K)

ENS is the core identity and discovery layer — the app does not work without it:

Subname registration: Every agent is registered as an ENS subname under the parent domain (e.g. myagent.a2app.eth) using the NameWrapper contract on Sepolia
12 text record keys per agent: agent-category, agent-description, agent-endpoint, agent-price, agent-capabilities, agent-credential, payment-address, world-nullifier, world-verification, agent-rating, agent-review-count, and a JSON metadata field
Agent discovery via ENS resolution: The explore page resolves all agents by reading their ENS text records through resolveAgentProfile() — no centralized index
Agent-to-agent resolution: When one agent composes with another, it resolves the target's ENS name to read endpoint, price, and credential metadata before paying
On-chain reputation on ENS: After reviews are submitted to Hedera HCS, aggregate ratings (average + count) are written back to the agent's ENS text records via updateAgentRatingRecords() so reputation is discoverable at resolution time
No hard-coded values: All agent metadata is read live from ENS. The marketplace is a view layer over ENS state

Arc — Agentic Economy with Nanopayments ($6K)

Full x402 nanopayment integration for agent-to-agent and human-to-agent commerce:

Server-side: x402ResourceServer + HTTPFacilitatorClient + ExactEvmScheme handle payment verification and settlement
Client-side: @x402/fetch wraps fetch with automatic 402 handling, @x402/evm provides ExactEvmScheme for EIP-3009 authorization signing via MiniKit.signTypedData()
Agent marketplace with micropayments: Each agent has a USDC price per request. Users pay per use — no subscriptions, no accounts, no credit cards
Agent-to-agent commerce: In the composition flow, one agent pays another agent's x402 endpoint autonomously. The caller resolves the target via ENS, reads the price, and the x402 client handles settlement
Payment receipts: Every x402 settlement returns a transaction hash displayed in the UI and logged to Hedera HCS as an immutable audit trail
Network-agnostic architecture: The x402 network is configurable via environment variables. Currently on Base Sepolia (where the x402.org facilitator is available); ready to switch to Arc Testnet (eip155:5042002) with a config change when the Arc facilitator goes live

See arc.md for a detailed breakdown of the x402 integration.

License

MIT

Name		Name	Last commit message	Last commit date
Latest commit History 24 Commits
contracts		contracts
web		web
.gitignore		.gitignore
.node-version		.node-version
README.md		README.md
arc.md		arc.md
architecture.md		architecture.md
package-lock.json		package-lock.json
package.json		package.json

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A2A — Verified AI Agent Marketplace

Why This Exists

How It Compares

Architecture

Tech Stack

Project Structure

Running Locally

Prerequisites

Step-by-step setup

Environment Variables

Smart contract deployment (optional)

Demo Flow

Bounty Eligibility

World — AgentKit ($8K) + World ID 4.0 ($8K) + MiniKit 2.0 ($4K)

ENS — Best ENS Integration for AI Agents ($5K)

Arc — Agentic Economy with Nanopayments ($6K)

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A2A — Verified AI Agent Marketplace

Why This Exists

How It Compares

Architecture

Tech Stack

Project Structure

Running Locally

Prerequisites

Step-by-step setup

Environment Variables

Smart contract deployment (optional)

Demo Flow

Bounty Eligibility

World — AgentKit ($8K) + World ID 4.0 ($8K) + MiniKit 2.0 ($4K)

ENS — Best ENS Integration for AI Agents ($5K)

Arc — Agentic Economy with Nanopayments ($6K)

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