ERC-8004: Agent Trust Protocol

ERC-8004 is an Ethereum standard that establishes trust infrastructure for autonomous AI agents. It enables agents to discover, identify, and evaluate other agents across organizational boundaries without pre-existing trust relationships.

Key Features

Identity Registry: Portable agent identifiers based on ERC-721 NFTs
Reputation Registry: Standardized feedback and rating system for agents
Validation Registry: Independent verification hooks where third-party validators can attest to agent outputs—supporting stake-secured re-execution, zkML proofs, or TEE attestations for high-stakes operations
Cross-Chain Support: Works on any EVM-compatible chain including Celo

Why ERC-8004?

When AI agents interact across organizational boundaries, three critical questions arise:

Discovery: How do agents find each other? The Identity Registry provides searchable metadata—agents query the registry to discover other agents by capabilities, endpoints, or domain.
Identity: How do agents verify who they’re dealing with? Each agent is an ERC-721 NFT with a cryptographically linked wallet, enabling verification that you’re communicating with the authentic agent owner.
Trust: How do agents evaluate reliability? The Reputation Registry stores feedback from every interaction, creating a portable track record that travels with the agent across platforms.

Protocol stack

ERC-8004 fits into the broader agent infrastructure stack:

The Three Registries

1. Identity Registry

Makes agents discoverable via portable NFT identifiers. Key capabilities:

Every agent identity is represented as an ERC-721 NFT—the agent itself runs off-chain, but its on-chain identity is an NFT that’s browsable in wallets, transferable between owners, and queryable by smart contracts
agentURI points to registration file with endpoints
Supports multiple endpoint types (A2A, MCP, wallet, ENS, DIDs)
Domain verification for endpoint ownership

Agent registration file structure:

{
  "type": "Agent",
  "name": "My AI Agent",
  "description": "Description of capabilities",
  "image": "ipfs://...",
  "endpoints": [
    {
      "type": "a2a",
      "url": "https://example.com/.well-known/agent.json"
    },
    {
      "type": "mcp",
      "url": "https://example.com/mcp"
    },
    {
      "type": "wallet",
      "address": "0x...",
      "chainId": 42220
    }
  ],
  "supportedTrust": ["reputation", "validation", "tee"]
}

2. Reputation Registry

Stores feedback and attestations about agent performance. Feedback is submitted on-chain by any address that has interacted with the agent—this includes users who hired the agent, other agents that collaborated with it, or monitoring services that track uptime and responsiveness. The contract prevents agents from rating themselves (owner and operator addresses are blocked from submitting feedback on their own agent). Common feedback tags:

Tag	Measures	Example
`starred`	Quality rating (0-100)	87/100
`uptime`	Endpoint uptime %	99.77%
`successRate`	Task success rate %	89%
`responseTime`	Response time (ms)	560ms
`reachable`	Endpoint reachable	true/false

Key functions:

giveFeedback() - Submit feedback with score and tags
revokeFeedback() - Remove previous feedback
readAllFeedback() - Get all feedback for an agent
getSummary() - Get aggregated reputation summary

3. Validation Registry

Independent verification hooks for high-stakes operations. Supported validation approaches:

Model	Mechanism	Best For
Reputation-based	Client feedback with scores	Low-stake, frequent interactions
Crypto-economic	Stake-secured validation with slashing	Medium-stake financial operations
zkML	Zero-knowledge proofs of correct execution	Privacy-preserving verification
TEE Attestation	Hardware-isolated execution proofs	High-assurance requirements

Check out the repository of the ERC-8004 protocol for agent discovery and trust through reputation and validation.

Contract Deployments

Celo Mainnet

Contract	Address
Identity Registry	0x8004A169FB4a3325136EB29fA0ceB6D2e539a432
Reputation Registry	0x8004BAa17C55a88189AE136b182e5fdA19dE9b63

Celo Sepolia (Testnet)

Contract	Address
Identity Registry	0x8004A818BFB912233c491871b3d84c89A494BD9e
Reputation Registry	0x8004B663056A597Dffe9eCcC1965A193B7388713

Quick Start

Install SDK

The ERC-8004 SDK provides TypeScript/JavaScript and Python interfaces to interact with the on-chain registries. Install the SDK for your preferred language:

# JavaScript/TypeScript
npm install @chaoschain/sdk

# Python
pip install chaoschain-sdk

Register an Agent

Registration mints a new ERC-721 NFT that represents your agent’s on-chain identity. You’ll need to:

Create a registration file (JSON) describing your agent’s name, capabilities, and endpoints
Upload it to IPFS or host it at a public URL
Call the registry to mint your agent NFT with the URI pointing to that file

import { IdentityRegistry } from '@chaoschain/sdk';

const registry = new IdentityRegistry(provider);

// Upload registration file to IPFS first
const agentURI = 'ipfs://QmYourRegistrationFile';

// Register and get agent ID
const tx = await registry.register(agentURI);
const agentId = tx.events.Transfer.returnValues.tokenId;

console.log('Agent registered with ID:', agentId);

Give Feedback

After interacting with an agent, submit feedback to the Reputation Registry. Each feedback entry includes a score, category tag (like “starred” for quality or “uptime” for availability), and an optional link to detailed off-chain feedback data:

import { ReputationRegistry } from '@chaoschain/sdk';

const reputation = new ReputationRegistry(provider);

await reputation.giveFeedback(
  agentId,
  85,                    // score (0-100)
  0,                     // decimals
  'starred',             // tag1: category
  '',                    // tag2: optional
  'https://agent.example.com',  // endpoint used
  'ipfs://QmDetailedFeedback',  // detailed feedback URI
  feedbackHash           // keccak256 of feedback content
);

Query Agent Reputation

Before delegating tasks to an agent, check its reputation. You can retrieve all individual feedback entries or get aggregated statistics:

// Get all feedback
const feedback = await reputation.readAllFeedback(agentId);

// Get summary statistics
const summary = await reputation.getSummary(agentId);
console.log('Average rating:', summary.averageScore);
console.log('Total reviews:', summary.totalFeedback);

Use Cases

DeFi Trading Agents

This diagram shows a typical agent-to-agent interaction flow. A portfolio management agent needs to execute a trade, so it:

Queries the Identity Registry to discover available strategy agents
Filters candidates using the Reputation Registry (checking track records, success rates)
Selects an agent and requests a trade
Pays for the service via x402 (HTTP-native payments)
After the trade completes, submits feedback to build the strategy agent’s reputation

Multi-Agent Workflows

AI agents collaborating across organizations can:

Discover each other via Identity Registry
Verify credentials before delegation
Track performance with Reputation Registry
Use Validation Registry for high-stakes decisions

Integration with Celo

ERC-8004 works seamlessly with Celo’s ecosystem:

Fee abstraction: Register agents and give feedback paying gas in stablecoins
x402 payments: Combine trust verification with instant payments
MCP servers: Agents can expose capabilities via Celo MCP Server

Resources

Resource	Link
EIP Specification	eips.ethereum.org/EIPS/eip-8004
Official Website	8004.org
Learning Portal	8004.org/learn
Contracts Repo	github.com/erc-8004/erc-8004-contracts
Telegram	t.me/ERC8004
Builder Program	bit.ly/8004builderprogram

x402 - Payment layer for AI agents
MPP - Machine Payments Protocol: charge USDC per request over HTTP
Celopedia - Celo ecosystem knowledge for coding assistants
MCP Servers - Connect agents to data and tools

Overview

Build with AI

Use Cases

Fee Abstraction

ERC-8004: Agent Trust Protocol

Key Features

Why ERC-8004?

Protocol stack

The Three Registries

1. Identity Registry

2. Reputation Registry

3. Validation Registry

Contract Deployments

Celo Mainnet

Celo Sepolia (Testnet)

Quick Start

Install SDK

Register an Agent

Give Feedback

Query Agent Reputation

Use Cases

DeFi Trading Agents

Multi-Agent Workflows

Integration with Celo

Resources

​Key Features

​Why ERC-8004?

​Protocol stack

​The Three Registries

​1. Identity Registry

​2. Reputation Registry

​3. Validation Registry

​Contract Deployments

​Celo Mainnet

​Celo Sepolia (Testnet)

​Quick Start

​Install SDK

​Register an Agent

​Give Feedback

​Query Agent Reputation

​Use Cases

​DeFi Trading Agents

​Multi-Agent Workflows

​Integration with Celo

​Resources

​Related Protocols

Key Features

Why ERC-8004?

Protocol stack

The Three Registries

1. Identity Registry

2. Reputation Registry

3. Validation Registry

Contract Deployments

Celo Mainnet

Celo Sepolia (Testnet)

Quick Start

Install SDK

Register an Agent

Give Feedback

Query Agent Reputation

Use Cases

DeFi Trading Agents

Multi-Agent Workflows

Integration with Celo

Resources

Related Protocols