ERC-8004 + feedbackAuth

Agent registration (EIP-7702) and feedbackAuth generation for on-chain reputation

The facilitator extends the x402 payment flow with ERC-8004 identity and reputation primitives:

• Agent registration: mint/register an agent identity on-chain (ERC-8004 Identity Registry)

• Feedback authorization (feedbackAuth): enable authenticated, client-submitted on-chain feedback after a paid request settles

Contracts

The facilitator needs contract addresses via env:

• ERC8004_IDENTITY_REGISTRY_ADDRESS: ERC-8004 Identity Registry

• DELEGATE_CONTRACT_ADDRESS: EIP-7702 delegation contract (see monorepo/facilitator/contracts/AgentRegistrationDelegate.sol)

ABIs are defined in monorepo/facilitator/src/config/contracts.ts.

Agent registration flow (EIP-7702)

Implementation: monorepo/facilitator/src/services/registerService.ts

1. Agent signs authorization delegating to the delegate contract (EIP-7702).

   • Example client code lives in monorepo/facilitator/examples/v1-server/index.ts and examples/v2-server/index.ts.

2. Client calls POST /register with:

   • agentAddress (the delegated EOA)

   • authorization (the signed authorization)

   • optional tokenURI + metadata

3. Facilitator sends an on-chain tx with:

   • authorizationList: [authorization]

   • to: agentAddress

   • data: encodeFunctionData(delegate.register(...))

4. Facilitator waits for receipt and decodes the Registered event to return agentId.

feedbackAuth flow (x402 v2 extension)

Implementation: monorepo/facilitator/src/services/feedbackService.ts plus the feedback extension hook in monorepo/facilitator/index.ts.

To request feedback auth generation, the paid resource should include an x402 v2 extension like:

{
  "extensions": {
    "feedback": {
      "feedbackEnabled": true,
      "agentId": "1234",
      "feedbackAuthEndpoint": "/signFeedbackAuth"
    }
  }
}

After a successful v2 settlement, the facilitator:

1. Extracts the payer address from the payment payload (authorization.from).

2. Reads ownerOf(agentId) from the Identity Registry to determine the signer address.

3. Builds a FeedbackAuth struct and computes the EIP-191 message hash.

4. Requests a signature from the agent server (intended via feedbackAuthEndpoint).

5. Stores { agentId, feedbackAuth } in-memory keyed by client address.

What is feedbackAuth?

In this implementation, feedbackAuth is encoded as:

1. abi.encode(FeedbackAuthStruct)

2. followed by a 65-byte ECDSA signature (r || s || v)

The struct fields (and ordering) are:

• agentId (uint256)

• clientAddress (address)

• indexLimit (uint64)

• expiry (uint256)

• chainId (uint256)

• identityRegistry (address)

• signerAddress (address)

Current limitations (implementation notes)

The facilitator repo’s TODO.md calls out a few important gaps:

• The v2 feedbackAuth is generated and stored in-memory, but not returned to the client yet.

• The facilitator will only request a signature from the agent server when it can derive an origin from paymentPayload.resource.url. If that URL is missing/invalid, it falls back to local signing.

• If the agent server can’t be reached, it falls back to signing with FACILITATOR_PRIVATE_KEY, which will not match ownerOf(agentId) unless the facilitator key is the agent owner key (and would produce an invalid signature on-chain).