ERC-8004: Trustless Agents on MegaETH

AI coding skill for implementing ERC-8004 (Trustless Agents) on MegaETH. Covers agent identity registration, reputation feedback, validation requests, and integration with A2A/MCP endpoints.

What This Skill Is For

Use this skill when the user asks for:

Registering an AI agent identity on-chain (ERC-721 based)
Setting up agent metadata, wallet verification, and registration files
Giving, reading, or revoking reputation feedback for agents
Requesting and recording validation of agent work
Building agent discovery and trust systems
Integrating ERC-8004 with A2A, MCP, or x402 payment protocols
Deploying ERC-8004 registries on MegaETH

Architecture Overview

ERC-8004 defines three singleton registries that can be deployed per chain:

Registry	Purpose
Identity Registry	ERC-721 NFT-based agent handles. Each agent gets a `tokenId` (agentId) and a `tokenURI` (agentURI) pointing to a registration file.
Reputation Registry	Standardized feedback signals — clients rate agents with signed fixed-point values, filterable by tags.
Validation Registry	Third-party verification hooks — agents request validation, validators respond with scores (0-100).

Chain Configuration

Network	Chain ID	RPC
MegaETH Mainnet	4326	`https://mainnet.megaeth.com/rpc`
MegaETH Testnet	6343	`https://carrot.megaeth.com/rpc`
Ethereum Mainnet	1	(reference deployment)

Contract Addresses (All Chains — CREATE2 Deterministic)

Deployed via CREATE2 — same addresses on every chain including MegaETH.

Contract	Mainnet Address	Testnet Address
Identity Registry	`0x8004A169FB4a3325136EB29fA0ceB6D2e539a432`	`0x8004A818BFB912233c491871b3d84c89A494BD9e`
Reputation Registry	`0x8004BAa17C55a88189AE136b182e5fdA19dE9b63`	`0x8004B663056A597Dffe9eCcC1965A193B7388713`

Explorers:

MegaETH Mainnet: Identity · Reputation
MegaETH Testnet: Identity · Reputation

Full deployment list: erc-8004/erc-8004-contracts

Default Stack Decisions (Opinionated)

1. Use `eth_sendRawTransactionSync` for all writes

MegaETH returns receipts in <10ms via EIP-7966. No polling needed after registration or feedback calls.

2. Use viem over ethers.js

The @agentic-trust/8004-sdk supports both. Prefer viem for consistency with MegaETH patterns.

3. Store registration files on IPFS or as on-chain data URIs

For fully on-chain agents, use data:application/json;base64,... as the agentURI. For off-chain, use IPFS for easy subgraph indexing.

4. Always verify agent wallet ownership

Use setAgentWallet() with an EIP-712 signature (EOA) or ERC-1271 (smart contract wallet) to prove control. The wallet auto-clears on NFT transfer.

SDK Installation

npm install @agentic-trust/8004-sdk viem

Agent Registration File

The agentURI resolves to a JSON registration file:

{
  "type": "https://eips.ethereum.org/EIPS/eip-8004#registration-v1",
  "name": "MyAgent",
  "description": "An autonomous trading agent on MegaETH",
  "image": "https://example.com/agent.png",
  "services": [
    {
      "name": "A2A",
      "endpoint": "https://agent.example/.well-known/agent-card.json",
      "version": "0.3.0"
    },
    {
      "name": "MCP",
      "endpoint": "https://mcp.agent.example/",
      "version": "2025-06-18"
    }
  ],
  "x402Support": true,
  "active": true,
  "registrations": [
    {
      "agentId": 1,
      "agentRegistry": "eip155:4326:0x8004A169FB4a3325136EB29fA0ceB6D2e539a432"
    }
  ],
  "supportedTrust": ["reputation"]
}

Required fields: type, name, description, image Recommended: At least one registrations entry and one service endpoint.

Identity Registry

Register an Agent

import { createWalletClient, http, encodePacked } from 'viem'

const IDENTITY_REGISTRY = '0x8004A169FB4a3325136EB29fA0ceB6D2e539a432'

// Minimal registration (set URI later)
const agentId = await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'register',
  args: []
})

// Registration with URI
const agentId = await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'register',
  args: ['ipfs://QmYourRegistrationFile']
})

// Registration with URI + metadata
const agentId = await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'register',
  args: [
    'ipfs://QmYourRegistrationFile',
    [{ metadataKey: 'version', metadataValue: '0x01' }]
  ]
})

Update Agent URI

await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'setAgentURI',
  args: [agentId, 'ipfs://QmNewRegistrationFile']
})

Fully On-Chain Registration

const registrationJson = JSON.stringify({
  type: "https://eips.ethereum.org/EIPS/eip-8004#registration-v1",
  name: "OnChainAgent",
  description: "Fully on-chain agent identity",
  image: "data:image/svg+xml;base64,...",
  services: [],
  active: true,
  registrations: [{ agentId: 1, agentRegistry: `eip155:4326:${IDENTITY_REGISTRY}` }]
})

const dataUri = `data:application/json;base64,${btoa(registrationJson)}`

await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'setAgentURI',
  args: [agentId, dataUri]
})

Set & Verify Agent Wallet

The agentWallet is where the agent receives payments. It requires a signature to prove ownership:

// For EOA wallets (EIP-712 signature)
await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'setAgentWallet',
  args: [agentId, newWalletAddress, deadline, signature]
})

// Read wallet
const wallet = await publicClient.readContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'getAgentWallet',
  args: [agentId]
})

On-Chain Metadata

// Set custom metadata
await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'setMetadata',
  args: [agentId, 'version', '0x0100'] // arbitrary bytes
})

// Read metadata
const data = await publicClient.readContract({
  address: IDENTITY_REGISTRY,
  abi: identityRegistryAbi,
  functionName: 'getMetadata',
  args: [agentId, 'version']
})

Endpoint Domain Verification (Optional)

Prove control of an HTTPS endpoint by hosting a .well-known file:

GET https://agent.example/.well-known/agent-registration.json

{
  "registrations": [
    {
      "agentId": 1,
      "agentRegistry": "eip155:4326:0x8004A169FB4a3325136EB29fA0ceB6D2e539a432"
    }
  ]
}

Reputation Registry

Give Feedback

Any address (except the agent owner) can give feedback:

const REPUTATION_REGISTRY = '0x8004BAa17C55a88189AE136b182e5fdA19dE9b63'

await walletClient.writeContract({
  address: REPUTATION_REGISTRY,
  abi: reputationRegistryAbi,
  functionName: 'giveFeedback',
  args: [
    agentId,            // uint256 — target agent
    87n,                // int128 — value (e.g., 87/100)
    0,                  // uint8 — valueDecimals (0 = integer)
    'starred',          // string — tag1 (category)
    '',                 // string — tag2 (optional)
    '',                 // string — endpoint (optional)
    'ipfs://QmFeedback', // string — feedbackURI (optional)
    '0x0000000000000000000000000000000000000000000000000000000000000000' // bytes32 — feedbackHash (optional, not needed for IPFS)
  ]
})

Common Feedback Patterns

tag1	What it measures	Example value	valueDecimals
`starred`	Quality rating (0-100)	87	0
`reachable`	Endpoint reachable (binary)	1	0
`uptime`	Endpoint uptime (%)	9977	2 (= 99.77%)
`successRate`	Success rate (%)	89	0
`responseTime`	Response time (ms)	560	0

Read Feedback

// Read specific feedback
const feedback = await publicClient.readContract({
  address: REPUTATION_REGISTRY,
  abi: reputationRegistryAbi,
  functionName: 'readFeedback',
  args: [agentId, clientAddress, feedbackIndex]
})
// Returns: { value, valueDecimals, tag1, tag2, isRevoked }

// Get aggregated summary (filtered by trusted clients)
const summary = await publicClient.readContract({
  address: REPUTATION_REGISTRY,
  abi: reputationRegistryAbi,
  functionName: 'getSummary',
  args: [agentId, trustedClientAddresses, 'starred', '']
})
// Returns: { count, summaryValue, summaryValueDecimals }

// Get all clients who gave feedback
const clients = await publicClient.readContract({
  address: REPUTATION_REGISTRY,
  abi: reputationRegistryAbi,
  functionName: 'getClients',
  args: [agentId]
})

Important: Always filter by clientAddresses when reading summaries. Unfiltered results are vulnerable to Sybil attacks.

Revoke Feedback

await walletClient.writeContract({
  address: REPUTATION_REGISTRY,
  abi: reputationRegistryAbi,
  functionName: 'revokeFeedback',
  args: [agentId, feedbackIndex]
})

Append Response

Anyone can append a response to feedback (e.g., agent showing a refund, spam tagger):

await walletClient.writeContract({
  address: REPUTATION_REGISTRY,
  abi: reputationRegistryAbi,
  functionName: 'appendResponse',
  args: [agentId, clientAddress, feedbackIndex, 'ipfs://QmResponse', '0x...']
})

Validation Registry

Request Validation

Agent owners request third-party validation of their work:

// Validation Registry not yet deployed — check erc-8004/erc-8004-contracts for updates
const VALIDATION_REGISTRY = '0x...'

await walletClient.writeContract({
  address: VALIDATION_REGISTRY,
  abi: validationRegistryAbi,
  functionName: 'validationRequest',
  args: [
    validatorContractAddress, // address — the validator
    agentId,                  // uint256
    'ipfs://QmRequestData',   // string — requestURI (inputs + outputs for verification)
    requestHash               // bytes32 — keccak256 of request payload
  ]
})

Respond to Validation (Validator Only)

// Called by the validator contract
await walletClient.writeContract({
  address: VALIDATION_REGISTRY,
  abi: validationRegistryAbi,
  functionName: 'validationResponse',
  args: [
    requestHash,      // bytes32
    100,              // uint8 — response (0=failed, 100=passed)
    'ipfs://QmAudit', // string — responseURI (optional)
    '0x...',          // bytes32 — responseHash (optional)
    'final'           // string — tag (optional, e.g., "soft-finality", "final")
  ]
})

Read Validation Status

const status = await publicClient.readContract({
  address: VALIDATION_REGISTRY,
  abi: validationRegistryAbi,
  functionName: 'getValidationStatus',
  args: [requestHash]
})
// Returns: { validatorAddress, agentId, response, responseHash, tag, lastUpdate }

// Aggregated stats
const summary = await publicClient.readContract({
  address: VALIDATION_REGISTRY,
  abi: validationRegistryAbi,
  functionName: 'getSummary',
  args: [agentId, validatorAddresses, '']
})
// Returns: { count, averageResponse }

Agent Global Identifier

Each agent is globally unique via:

agentRegistry: eip155:{chainId}:{identityRegistryAddress}
agentId: {tokenId}

For MegaETH mainnet:

eip155:4326:0x8004A169FB4a3325136EB29fA0ceB6D2e539a432

An agent registered on MegaETH can operate and transact on any chain. Multi-chain registration is also supported.

Off-Chain Feedback File

Optional detailed feedback stored on IPFS:

{
  "agentRegistry": "eip155:4326:0x8004A169FB4a3325136EB29fA0ceB6D2e539a432",
  "agentId": 1,
  "clientAddress": "eip155:4326:0xClientAddr",
  "createdAt": "2026-03-12T00:00:00Z",
  "value": 95,
  "valueDecimals": 0,
  "tag1": "starred",
  "endpoint": "https://agent.example/api",
  "mcp": { "tool": "GetPrice" },
  "proofOfPayment": {
    "fromAddress": "0x...",
    "toAddress": "0x...",
    "chainId": "4326",
    "txHash": "0x..."
  }
}

MegaETH-Specific Notes

Gas: Registration mints an ERC-721 (new storage slots). Use eth_estimateGas via RPC — MegaETH SSTORE costs differ from standard EVM.
Instant receipts: Use eth_sendRawTransactionSync (EIP-7966) for all write operations.
State growth: Each new agent identity creates storage slots. Be aware of MegaETH's 1,000 slot per-tx limit for batch operations.
Subgraphs: Feedback data is stored on-chain + emitted as events. Use subgraphs or event indexing for efficient querying.
Sybil resistance: Always filter reputation queries by trusted clientAddresses. Unfiltered getSummary calls are meaningless.

Related Standards

Standard	Relationship
ERC-721	Identity Registry is ERC-721 based
EIP-712	Wallet verification signatures
ERC-1271	Smart contract wallet verification
x402	Payment proof in feedback signals
A2A	Agent-to-agent communication (advertised in registration)
MCP	Model context protocol (advertised in registration)

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ERC-8004: Trustless Agents on MegaETH

What This Skill Is For

Architecture Overview

Chain Configuration

Contract Addresses (All Chains — CREATE2 Deterministic)

Default Stack Decisions (Opinionated)

1. Use `eth_sendRawTransactionSync` for all writes

2. Use viem over ethers.js

3. Store registration files on IPFS or as on-chain data URIs

4. Always verify agent wallet ownership

SDK Installation

Agent Registration File

Identity Registry

Register an Agent

Update Agent URI

Fully On-Chain Registration

Set & Verify Agent Wallet

On-Chain Metadata

Endpoint Domain Verification (Optional)

Reputation Registry

Give Feedback

Common Feedback Patterns

Read Feedback

Revoke Feedback

Append Response

Validation Registry

Request Validation

Respond to Validation (Validator Only)

Read Validation Status

Agent Global Identifier

Off-Chain Feedback File

MegaETH-Specific Notes

Related Standards

Resources

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erc8004-trustless-agents.md

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erc8004-trustless-agents.md

File metadata and controls

ERC-8004: Trustless Agents on MegaETH

What This Skill Is For

Architecture Overview

Chain Configuration

Contract Addresses (All Chains — CREATE2 Deterministic)

Default Stack Decisions (Opinionated)

1. Use eth_sendRawTransactionSync for all writes

2. Use viem over ethers.js

3. Store registration files on IPFS or as on-chain data URIs

4. Always verify agent wallet ownership

SDK Installation

Agent Registration File

Identity Registry

Register an Agent

Update Agent URI

Fully On-Chain Registration

Set & Verify Agent Wallet

On-Chain Metadata

Endpoint Domain Verification (Optional)

Reputation Registry

Give Feedback

Common Feedback Patterns

Read Feedback

Revoke Feedback

Append Response

Validation Registry

Request Validation

Respond to Validation (Validator Only)

Read Validation Status

Agent Global Identifier

Off-Chain Feedback File

MegaETH-Specific Notes

Related Standards

Resources

1. Use `eth_sendRawTransactionSync` for all writes