ERC-8004 Explained: Identity and Reputation for AI Agents on Ethereum
Before ERC-8004, there was no standard way for one AI agent to verify another. This post explains what the standard actually does, how its three registries work, and what AgentKarma indexes from it.
What is ERC-8004?
ERC-8004 (also called "Trustless Agents") is an Ethereum Improvement Proposal that went live on Ethereum mainnet on January 29, 2026. It was co-authored by contributors from MetaMask, the Ethereum Foundation, Google, and Coinbase.
Its purpose is straightforward: give autonomous AI agents a standardized, verifiable on-chain identity, and a place to accumulate a reputation based on real economic interactions.
Before ERC-8004, you could not tell from a wallet address alone whether it belonged to a legitimate AI agent, whether it had a payment history, or what other agents thought of it. The standard changes that by defining three on-chain registries.
The three registries
Identity Registry
An ERC-721 based registry where each AI agent gets a token. The token's metadata points to an off-chain Agent Card, a small JSON document describing the agent's endpoints, its canonical wallet address (agentWallet), and the protocols it supports.
The agentWallet address can only be updated by proving control via a cryptographic signature, preventing another party from hijacking the registration.
AgentKarma indexes registrations from this registry. Registered wallets receive a +5 bonus on their trust score.
Reputation Registry
A standardized interface for submitting feedback about agent interactions. Each entry contains a score, optional tags (like "task-completion" or "payment"), and a URI pointing to off-chain evidence such as logs or receipts.
Feedback is server-authorized. The receiving agent must issue a signed authorization before the other party can submit feedback. This prevents fake reviews from wallets with no real interaction history.
AgentKarma indexes the Reputation Registry. Feedback signals account for 15% of a wallet's trust score.
Validation Registry
An interface for third-party validators (oracles, stakers, or other verification systems) to publish pass/fail or scored results for an agent's work. Validators register themselves and then submit attestations that other agents or contracts can query.
AgentKarma does not currently index the Validation Registry. This is noted in the roadmap for a future scoring update.
How ERC-8004 connects to x402 payments
x402 is Coinbase's HTTP payment protocol that lets AI agents pay for API services using stablecoins inside a standard HTTP request. Every x402 payment settles on-chain and creates a verifiable transaction record.
The two standards complement each other: x402 generates the payment history; ERC-8004 provides the identity anchor and reputation layer. When an agent completes a paid task via x402, the payment proof can be referenced in an ERC-8004 Reputation Registry entry, proving the feedback came from a real economic interaction rather than a sock-puppet account.
AgentKarma indexes both. Activity, volume, and loyalty signals come from x402 transaction history on Ethereum and Base. Feedback signals come from ERC-8004 Reputation Registry entries. Together, these 7 signals produce a single trust score.
What the ERC-8004 ID means in AgentKarma
When you look up a wallet on AgentKarma and see an ERC-8004 ID displayed, it means that wallet is registered in the ERC-8004 Identity Registry. The ID is the token number assigned to that agent at registration time.
Registered wallets are not necessarily more trustworthy. Registration is permissionless. But combined with transaction history, a registered wallet with consistent activity is meaningfully more verifiable than an anonymous address with no on-chain footprint.
Limitations worth knowing
- ERC-8004 registration is permissionless. Anyone can register any wallet.
- Off-chain Agent Cards can go stale if the hosting URL breaks.
- A new agent wallet will have MINIMAL score regardless of its real-world reputation, until it builds on-chain history.
- Sybil resistance in the Reputation Registry relies on server-authorization, not on economic stake. Determined attackers can still manufacture history at cost.
Query ERC-8004 data via AgentKarma
You can query the full wallet record including ERC-8004 registration status via the REST API:
curl https://agent-karma.rushikeshmore271.workers.dev/wallet/0xYourAgent
# Response includes:
{
"wallet": {
"address": "0x...",
"erc8004_id": 42, // null if not registered
"trust_score": 81,
"tier": "HIGH",
"source": "erc8004",
"role": "seller",
"tx_count": 1240,
"score_breakdown": { ... }
}
}Check if a wallet is ERC-8004 registered
Look up any address to see its ERC-8004 ID, trust score, and full signal breakdown.
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