ERC-8004

ERC-8004 is the Agent Identity Standard for Ethereum that enables discovering, choosing, and interacting with agents across organizational boundaries without pre-existing trust.

What is ERC-8004?

ERC-8004 provides a standard way to represent AI agent identities on Ethereum using three core registries:

Identity Registry - ERC-721 NFTs for unique agent identities
Reputation Registry - Feedback and reputation tracking
Validation Registry - Third-party validator attestations This enables permissionless agent discovery, censorship-resistant identity, and interoperable trust signals across platforms.

Specification

📖 Read the full ERC-8004 specification

Contracts

The official ERC-8004 contracts are maintained by the 8004 team:

🔗 ERC-8004 Contracts Repository

Testnet Contract Addresses

ETH Sepolia

IdentityRegistry: 0x8004A818BFB912233c491871b3d84c89A494BD9e
ReputationRegistry: 0x8004B663056A597Dffe9eCcC1965A193B7388713
ValidationRegistry: not deployed in SDK defaults yet

Other networks may be available in the ERC-8004 ecosystem, but are not enabled in Agent0 SDK defaults yet.

Contract Functions

Identity Registry

Registration Functions:

register() → uint256 agentId
register(string agentURI) → uint256 agentId
register(string agentURI, MetadataEntry[] metadata) → uint256 agentId

Management Functions:

setAgentURI(uint256 agentId, string newURI)
setMetadata(uint256 agentId, string metadataKey, bytes metadataValue)
getMetadata(uint256 agentId, string metadataKey) → bytes

Reserved Metadata Key:

agentWallet is reserved and cannot be set via setMetadata() nor during register().
It is updated via signature verification:
- via the SDK: agent.setWallet(newWallet, ...)
- via the SDK: agent.unsetWallet()

ERC-721 Functions:

approve(address to, uint256 tokenId)
setApprovalForAll(address operator, bool approved)
transferFrom(address from, address to, uint256 tokenId)
safeTransferFrom(address from, address to, uint256 tokenId)
safeTransferFrom(address from, address to, uint256 tokenId, bytes data)

View Functions:

balanceOf(address owner) → uint256
ownerOf(uint256 tokenId) → address
getApproved(uint256 tokenId) → address
isApprovedForAll(address owner, address operator) → bool
tokenURI(uint256 tokenId) → string
name() → string
symbol() → string
supportsInterface(bytes4 interfaceId) → bool

Admin Functions:

owner() → address
transferOwnership(address newOwner)
renounceOwnership()
upgradeToAndCall(address newImplementation, bytes data)

Reputation Registry

Feedback Functions:

giveFeedback(uint256 agentId, int128 value, uint8 valueDecimals, string tag1, string tag2, string endpoint, string feedbackURI, bytes32 feedbackHash)
revokeFeedback(uint256 agentId, uint64 feedbackIndex)
appendResponse(uint256 agentId, address clientAddress, uint64 feedbackIndex, string responseURI, bytes32 responseHash)

Query Functions:

readFeedback(uint256 agentId, address clientAddress, uint64 feedbackIndex) → (int128 value, uint8 valueDecimals, string tag1, string tag2, bool isRevoked)
readAllFeedback(uint256 agentId, address[] clientAddresses, string tag1, string tag2, bool includeRevoked) → (address[] clientAddresses, uint64[] feedbackIndexes, int128[] values, uint8[] valueDecimals, string[] tag1s, string[] tag2s, bool[] revokedStatuses)
getSummary(uint256 agentId, address[] clientAddresses, string tag1, string tag2) → (uint64 count, int128 summaryValue, uint8 summaryValueDecimals)
getClients(uint256 agentId) → address[]
getLastIndex(uint256 agentId, address clientAddress) → uint64
getResponseCount(uint256 agentId, address clientAddress, uint64 feedbackIndex, address[] responders) → uint64 count

Admin Functions:

getIdentityRegistry → address
owner() → address
transferOwnership(address newOwner)
renounceOwnership()
upgradeToAndCall(address newImplementation, bytes data)

Validation Registry

Validation Functions:

validationRequest(address validatorAddress, uint256 agentId, string requestUri, bytes32 requestHash)
validationResponse(bytes32 requestHash, uint8 response, string responseUri, bytes32 responseHash, bytes32 tag)

Query Functions:

getValidationStatus(bytes32 requestHash) → (address validatorAddress, uint256 agentId, uint8 response, bytes32 responseHash, bytes32 tag, uint256 lastUpdate)
getSummary(uint256 agentId, address[] validatorAddresses, bytes32 tag) → (uint64 count, uint8 avgResponse)
getAgentValidations(uint256 agentId) → bytes32[]
getValidatorRequests(address validatorAddress) → bytes32[]
validations(bytes32) → (address validatorAddress, uint256 agentId, uint8 response, bytes32 responseHash, bytes32 tag, uint256 lastUpdate)

Admin Functions:

getIdentityRegistry → address
owner() → address
transferOwnership(address newOwner)
renounceOwnership()
upgradeToAndCall(address newImplementation, bytes data)

File Examples

Registration File

{
  "type": "https://eips.ethereum.org/EIPS/eip-8004#registration-v1",
  "name": "myAgentName",
  "description": "A natural language description of the Agent, which MAY include what it does, how it works, pricing, and interaction methods",
  "image": "https://example.com/agentimage.png",
  "endpoints": [
    {
      "name": "web",
      "endpoint": "https://web.agentxyz.com/"
    },
    {
      "name": "A2A",
      "endpoint": "https://agent.example/.well-known/agent-card.json",
      "version": "0.3.0"
    },
    {
      "name": "MCP",
      "endpoint": "https://mcp.agent.eth/",
      "capabilities": [],
      "version": "2025-06-18"
    },
    {
      "name": "OASF",
      "endpoint": "ipfs://{cid}",
      "version": "0.8",
      "skills": [],
      "domains": []
    },
    {
      "name": "ENS",
      "endpoint": "vitalik.eth",
      "version": "v1"
    },
    {
      "name": "DID",
      "endpoint": "did:method:foobar",
      "version": "v1"
    },
    {
      "name": "email",
      "endpoint": "mail@myagent.com"
    }
  ],
  "x402Support": false,
  "active": true,
  "registrations": [
    {
      "agentId": 22,
      "agentRegistry": "{namespace}:{chainId}:{identityRegistry}"
    }
  ],
  "supportedTrust": [
    "reputation",
    "crypto-economic",
    "tee-attestation"
  ]
}

Endpoint Domain Verification (Optional)

An agent MAY optionally prove control of an HTTPS endpoint-domain by publishing:

https://{endpoint-domain}/.well-known/agent-registration.json

Verifiers MAY treat the endpoint-domain as verified if the file is reachable over HTTPS and includes a registrations entry whose agentRegistry and agentId match the on-chain agent.

Feedback File

{
  "agentRegistry": "eip155:1:{identityRegistry}",
  "agentId": 22,
  "clientAddress": "eip155:1:{clientAddress}",
  "createdAt": "2025-09-23T12:00:00Z",
  "value": "100",
  "valueDecimals": 0,
  "tag1": "foo",
  "tag2": "bar",
  "endpoint": "https://.../",
  "skill": "as-defined-by-A2A-or-OASF",
  "domain": "as-defined-by-OASF",
  "context": "as-defined-by-A2A",
  "task": "as-defined-by-A2A",
  "capability": "tools",
  "name": "foo",
  "proofOfPayment": {
    "fromAddress": "0x00...",
    "toAddress": "0x00...",
    "chainId": "1",
    "txHash": "0x00..."
  }
}

Next Steps

Breaking change (Jan 2026): ERC-8004 reputation no longer uses a single score field.
- On-chain: reputation is represented as (value:int128, valueDecimals:uint8) for signed decimal precision.
- SDK: Agent0 SDK APIs accept/return a decoded signed decimal value.
- Off-chain: feedback files use value + valueDecimals (not score).
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