ERC-8004 — On-Chain Agent Registry

How AstraSync implements ERC-8004 for on-chain agent registration, identity resolution, and trust frameworks.

ERC-8004 defines an on-chain Agent Registry where each agent is an ERC-721 token. The token's tokenURI (called agentURI) points to an off-chain Agent Registration File — a JSON document describing the agent's services, trust frameworks, and identity.

AstraSync wraps ERC-8004 with Know Your Agent (KYA) verification and PDLSS permission boundaries, adding pre-execution governance to the spec's post-execution reputation model.

What AstraSync Built (PR #329)

PR #329 added ERC-8004 as a first-class protocol option:

• Protocol selection in the agent registration form
• Chain, registry, operator, and token ID fields
• Blockchain service integration for SKALE Base Sepolia
• Agent detail page display for ERC-8004 metadata

What PR #329 did NOT do: produce a spec-compliant Agent Registration File, interact with Reputation/Validation Registries, or perform smart contract operations. Those are addressed in subsequent phases.

Agent Registration File Schema

The Agent Registration File is the JSON served at an agent's agentURI. AstraSync's card generator produces this spec-compliant format for ERC-8004 agents:

{
  "type": "https://eips.ethereum.org/EIPS/eip-8004#registration-v1",
  "name": "My Agent",
  "description": "An AI agent registered on-chain",
  "image": "https://example.com/agent-avatar.png",
  "services": [
    { "name": "web", "endpoint": "https://api.example.com/agent", "version": "1.0" },
    { "name": "A2A", "endpoint": "https://api.example.com/a2a" },
    { "name": "MCP", "endpoint": "https://api.example.com/mcp", "version": "2025-03-26" }
  ],
  "x402Support": false,
  "active": true,
  "registrations": [
    {
      "agentId": 42,
      "agentRegistry": "eip155:1187947933:0x8004A169FB4a3325136EB29fA0ceB6D2e539a432"
    }
  ],
  "supportedTrust": ["reputation", "astrasync-pdlss"],
  "astrasyncId": "ASTRA-abc123...",
  "pdlss": { "...": "..." }
}

Services Field Guide

Each entry in services[] declares an endpoint where the agent can be reached:

OASF services additionally support skills[] (capability identifiers) and domains[] (operational domains) — these fields are hidden for other service types.

x402 Support

The x402Support field is a developer declaration indicating whether the agent supports the x402 payment protocol for HTTP-based micropayments.

AstraSync does not verify this claim. False declarations may affect the agent's trust score in future reputation system integrations.

Supported Trust Frameworks

The supportedTrust field declares which trust frameworks the agent participates in:

When PDLSS boundaries are configured during registration, astrasync-pdlss is automatically selected.

Agent Token ID & Registrations

Each ERC-8004 agent has two identifiers:

• ERC-721 Token ID (agentTokenId) — the on-chain canonical identifier, assigned after smart contract registration
• ASTRA-X ID (astrasyncIdLevel1) — AstraSync's internal platform identifier for routing and queries

The registrations[] array in the Agent Registration File uses CAIP-10 format: eip155:{chainId}:{registryAddress}.

The Token ID is not required at registration time — agents can register on AstraSync first and receive a Token ID after on-chain registration. The agent detail page shows whichever identifier is available.

Chain Support

Currently supported: SKALE Base Mainnet (chain ID 1187947933).

• Identity Registry: 0x8004A169FB4a3325136EB29fA0ceB6D2e539a432
• Reputation Registry: 0x8004BAa17C55a88189AE136b182e5fdA19dE9b63

On-chain vs off-chain: AstraSync handles agent registration, verification, and metadata (off-chain). Smart contract interactions (on-chain) for Identity Registry registration, reputation writes, and token transfers are Phase 2 scope.

PDLSS + ERC-8004: Complete Trust Lifecycle

ERC-8004's reputation model is post-execution — trust scores update after agent actions. AstraSync's PDLSS framework provides pre-execution governance: permission boundaries that constrain what an agent can do before it acts. Together they form a complete trust lifecycle:

1. Pre-execution (PDLSS) — Purpose, Duration, Limits, Scope, Self-instantiation boundaries
2. Execution — Agent operates within PDLSS boundaries
3. Post-execution (ERC-8004 Reputation) — Counterparties submit on-chain feedback

Coming Soon (Phase 2)

• Reputation Registry lifecycle writes (giveFeedback() at 5 lifecycle events)
• Hosted registration file endpoint (auto-populate tokenURI via setAgentURI())
• Auto-registration SDK for programmatic agent creation
• Multi-chain support beyond SKALE Base Sepolia
• astrasync-pdlss spec extension proposal to ERC-8004 authors