What Is ERC-8004?

Origin and authors

ERC-8004 was authored by Marco De Rossi and Davide Crapis, with substantial contribution from the Ethereum Foundation's dAI team and the Trustless Agents Working Group. The standard moved from initial proposal to draft to final status over a roughly nine-month discussion period on the Ethereum Magicians forum, finalizing in early 2026.

The motivation was practical. By late 2025, multiple registries were claiming to be the canonical place to register an AI agent, and the resulting fragmentation made it impossible to build any cross-platform tool. An agent in registry A could not easily be referenced from registry B. Reputation in one ecosystem did not travel to another. Identity providers were monetizing access to their own walled garden.

ERC-8004 was the response to that fragmentation: a permissionless, on-chain primitive that any agent can register against and any tool can read from, with no centralized intermediary.

What ERC-8004 specifies

The standard defines three components, each implemented as a smart contract or convention.

Identity Registry

A smart contract that maintains a mapping between agent IDs and owner wallets. When a new agent is registered, the contract issues an integer ID that is globally unique within that contract instance and immutable. The owner wallet can update an agent's metadata pointer (the agentURI), transfer ownership, or revoke the registration.

The Identity Registry is deployed at a known address on each supported chain. Reading from it is permissionless: any tool can enumerate registered agents, look up an agent's metadata, or verify ownership.

Reputation Registry

A separate smart contract that records feedback events about agents. Each feedback event carries a numeric value, a sender address, a target agent ID, and a timestamp. Sender attestations are cryptographically signed, so feedback cannot be forged or misattributed.

The Reputation Registry does not produce a score. It records facts about events. Aggregating those events into a useful reputation signal is the job of any service consuming the registry, including but not limited to independent rating providers like Treebeard.

agentURI metadata format

The agentURI is a string pointing to off-chain metadata. The URI scheme can be a data URI (base64-encoded JSON inline), an IPFS URI (decentralized storage), or an HTTPS URL (typical web hosting). The metadata format itself is JSON with a documented schema that includes:

• Display name and description
• Service endpoints (callable URLs, websocket endpoints, etc.)
• Supported capabilities and protocols
• Contact information for the operator
• References to other on-chain identifiers (token contracts, ENS names, etc.)

The on-chain Identity Registry stores only the agentURI string, not the metadata itself. This keeps gas costs low and gives operators flexibility about where to host the metadata.

Why a standard matters here

Software standards work when they let independent parties build against the same primitive without coordinating with each other. HTTP let anyone publish a website without permission from a central web service. SMTP let anyone send email without a relationship to the recipient's mail provider. ERC-20 let anyone issue a fungible token that any wallet could display.

ERC-8004 occupies the same role for AI agents. With ERC-8004, you can:

• Register an agent once and have it referenceable from any compatible tool, registry, or rating service.
• Receive feedback events at a stable identifier that does not change if you switch hosting providers or change your endpoint.
• Verify the cryptographic identity of an agent independently of any particular registrar.
• Move ownership or update metadata without requiring downstream consumers to re-register.

Without a standard, every agent ecosystem builds its own identity primitive, every tool has to integrate against multiple incompatible APIs, and reputation is non-portable. ERC-8004 ended that fragmentation for the part of the agent stack it covers.

Identity is not quality

One of the most common mistakes is to treat ERC-8004 registration as a quality signal. It is not. Registration is permissionless and free. Anyone can register an agent in two transactions. The registration tells you the agent exists. It tells you nothing about whether the agent does what it claims, whether the code is audited, whether the operator is reputable, or whether the economics are honest.

The numbers make this concrete. As of April 2026, Treebeard indexes more than 176,000 ERC-8004 agents across 14 chains. Of those, fewer than 0.05 percent earn a passing grade on independent rating. The remaining 99.96 percent are registered but have not yet generated the operational, reputation, or code signals that would justify higher trust.

ERC-8004 gives the agent a stable address. What happens at that address is the question independent rating exists to answer. How to evaluate whether an AI agent is trustworthy covers the seven-signal framework that distinguishes a registered agent from a trustworthy one.

How it works in practice

For an agent operator, the workflow looks like this:

1. Build the agent. Decide what services it offers, what endpoints it exposes, and what capabilities it claims.
2. Compose the metadata as JSON, following the agentURI schema. Either inline as base64 data URI, upload to IPFS, or host on HTTPS.
3. Call register() on the Identity Registry contract on the chain you operate on. The transaction returns the agent ID.
4. Begin operating. Other systems can now look up your agent by ID. Feedback events recorded against your ID accrue in the Reputation Registry. Independent rating services index you and produce ratings using public methodology.
5. When you ship updates, point the Identity Registry to a new agentURI. Your agent ID stays stable across changes.

For a counterparty evaluating an agent, the workflow is the inverse. Look up the agent ID in the Identity Registry to get the metadata. Read feedback events from the Reputation Registry for that ID. Cross-reference with independent ratings that aggregate signals from ERC-8004 plus other sources.

How it relates to other agent standards

ERC-8004 is one component of the agent commerce stack. Other standards address adjacent problems:

The stack is composable. An agent registered under ERC-8004 can transact via x402, record commerce events under ERC-8183, and operate within the permissions defined by an ERC-7710 delegation. Each standard solves one problem cleanly without overlapping the others.

FAQ

Sources

• EIP-8004: Trustless Agents Standard. Canonical Ethereum specification.
• Ethereum Magicians forum. Discussion archive for the standard's development.
• Treebeard Methodology. How Treebeard processes ERC-8004 reputation events into composite ratings.
• How to Evaluate Whether an AI Agent Is Trustworthy. The seven-signal framework that turns ERC-8004 identity into trust assessment.
• Treebeard Agent Directory. Searchable index of 176,000 plus rated ERC-8004 agents.