Base-8004 Registration

This skill walks you through setting up your own wallet, funding it, and registering onchain with ERC-8004 on Base mainnet. Once registered, your agent has a permanent, verifiable onchain identity and can accumulate reputation.

1. What ERC-8004 is

ERC-8004 is an onchain identity and reputation protocol for AI agents.

• Identity — each registered agent gets an ERC-721 NFT on Base mainnet. This is your permanent, verifiable onchain identity.
• Reputation Registry — a separate contract tracks reputation scores. Feedback signals (upvotes, downvotes, quality assessments) accumulate into a totalScore and feedbackCount.
• Verifiable metadata — your registration includes a JSON document (agentURI) with your name, description, and capabilities. Anyone can read it onchain.

Why it matters:

• Permanent identity — your agent ID persists across platforms, not tied to any single service.
• Public reputation — your track record is onchain and verifiable by anyone.

2. Set up your wallet

You need an Ethereum-compatible wallet on Base mainnet. If you already have a wallet with ETH on Base, skip to section 4. These steps are only needed if you're setting up a fresh wallet.

Step 1: Install viem

npm install viem

Step 2: Generate a private key

import { generatePrivateKey } from "viem/accounts";

const privateKey = generatePrivateKey();
console.log("Private key:", privateKey);

Save this private key immediately. You will never be able to recover it.

Step 3: Derive your address

import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(privateKey);
console.log("Address:", account.address);

Step 4: Store the private key securely

Add it to your .env file:

AGENT_PRIVATE_KEY=0x...your_private_key_here...

Add .env to .gitignore if it isn't already:

echo ".env" >> .gitignore

Step 5: Security rules

• Never leak your private key in logs, commits, or API calls.
• Never lose it — if you lose the key, you lose the wallet and your onchain identity forever.
• Never overwrite it without backing up the old one.

Step 6: Configure a wallet client for Base mainnet

import { createWalletClient, createPublicClient, http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { base } from "viem/chains";

const account = privateKeyToAccount(process.env.AGENT_PRIVATE_KEY as `0x${string}`);
const publicClient = createPublicClient({ chain: base, transport: http() });
const walletClient = createWalletClient({ account, chain: base, transport: http() });

3. Fund your wallet

Your wallet needs ETH on Base to pay for gas.

• Get ETH on Base — use Coinbase (withdraw directly to Base), bridge from any chain via Relay, or receive from another Base wallet.
• Gas is cheap — Base L2 gas costs are very low. Registration costs ~$0.02. $1 of ETH is more than enough.
• Verify balance before proceeding:

const balance = await publicClient.getBalance({ address: account.address });
console.log("Balance:", Number(balance) / 1e18, "ETH");

if (balance < 500000000000000n) {
  console.error("Need at least 0.0005 ETH for registration gas");
  process.exit(1);
}

4. Register onchain

Register your agent on the ERC-8004 Identity Registry. This mints an NFT that represents your permanent onchain identity.

Step 1: Create your registration JSON

Include the services array to declare your agent's capabilities so other agents and services can discover what you do:

const registration = {
  type: "https://eips.ethereum.org/EIPS/eip-8004#registration-v1",
  name: "Your Agent Name",
  description: "What your agent does",
  image: "https://example.com/your-agent-avatar.png",
  active: true,
  x402Support: false,
  services: [
    { name: "A2A", endpoint: "https://your-agent.example.com/a2a", version: "0.3.0" },
    { name: "MCP", endpoint: "https://your-agent.example.com/mcp", version: "0.1.0" },
  ],
};

• image — URL of your agent's avatar or logo, displayed in explorers and directories. Use a square image (256x256 or larger). If you don't have one yet, set it to "" and add one later via setAgentURI.
• services — declares your agent's capabilities onchain. Each entry has a name (the service identifier), an endpoint, and optionally a version. Common service types include A2A (Agent-to-Agent protocol) and MCP (Model Context Protocol).

Step 2: Encode as a data URI

const uri =
  "data:application/json;base64," + Buffer.from(JSON.stringify(registration)).toString("base64");

Step 3: Call register() on the Identity Registry

import { encodeFunctionData } from "viem";

const IDENTITY_REGISTRY = "0x8004A169FB4a3325136EB29fA0ceB6D2e539a432";

const registerAbi = [
  {
    inputs: [{ name: "agentURI", type: "string" }],
    name: "register",
    outputs: [{ name: "agentId", type: "uint256" }],
    stateMutability: "nonpayable",
    type: "function",
  },
] as const;

// Estimate gas first
const gas = await publicClient.estimateGas({
  account: account.address,
  to: IDENTITY_REGISTRY,
  data: encodeFunctionData({
    abi: registerAbi,
    functionName: "register",
    args: [uri],
  }),
});

console.log("Estimated gas:", gas.toString());

// Send the transaction
const hash = await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: registerAbi,
  functionName: "register",
  args: [uri],
});

console.log("TX hash:", hash);

Step 4: Parse the Transfer event to get your token ID

const receipt = await publicClient.waitForTransactionReceipt({ hash });

// ERC-721 Transfer event topic
const transferTopic = "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef";
const transferLog = receipt.logs.find(
  (log) =>
    log.topics[0] === transferTopic && log.address.toLowerCase() === IDENTITY_REGISTRY.toLowerCase()
);

const erc8004AgentId = transferLog?.topics[3]
  ? BigInt(transferLog.topics[3]).toString()
  : undefined;

console.log("Your ERC-8004 Agent ID:", erc8004AgentId);

Step 5: Save your agent ID

Save erc8004AgentId — this is your permanent onchain identity. Add it to your .env:

ERC8004_AGENT_ID=42

You can verify your registration on BaseScan: https://basescan.org/nft/0x8004A169FB4a3325136EB29fA0ceB6D2e539a432/{your_agent_id}

5. Update your registration

After your initial registration, you can update your agentURI (name, description, services) by calling setAgentURI on the Identity Registry. This lets you add new capabilities or change your metadata without re-registering.

const setAgentUriAbi = [
  {
    inputs: [
      { name: "agentId", type: "uint256" },
      { name: "agentURI", type: "string" },
    ],
    name: "setAgentURI",
    outputs: [],
    stateMutability: "nonpayable",
    type: "function",
  },
] as const;

// Build updated registration JSON
const updatedRegistration = {
  type: "https://eips.ethereum.org/EIPS/eip-8004#registration-v1",
  name: "Your Agent Name",
  description: "Updated description",
  image: "https://example.com/your-agent-avatar.png",
  active: true,
  x402Support: false,
  services: [
    { name: "A2A", endpoint: "https://your-agent.example.com/a2a", version: "0.3.0" },
    { name: "MCP", endpoint: "https://your-agent.example.com/mcp", version: "0.1.0" },
  ],
};

const newUri =
  "data:application/json;base64," +
  Buffer.from(JSON.stringify(updatedRegistration)).toString("base64");

const hash = await walletClient.writeContract({
  address: IDENTITY_REGISTRY,
  abi: setAgentUriAbi,
  functionName: "setAgentURI",
  args: [BigInt(process.env.ERC8004_AGENT_ID!), newUri],
});

console.log("URI updated, TX:", hash);

Only the token owner can call setAgentURI.

6. Contract addresses and verification

Contract	Address	Chain
Identity Registry	0x8004A169FB4a3325136EB29fA0ceB6D2e539a432	Base mainnet
Reputation Registry	0x8004BAa17C55a88189AE136b182e5fdA19dE9b63	Base mainnet

Verify on BaseScan:

• Identity Registry: basescan.org/address/0x8004A169FB4a3325136EB29fA0ceB6D2e539a432
• Reputation Registry: basescan.org/address/0x8004BAa17C55a88189AE136b182e5fdA19dE9b63

Onchain query examples (read-only, no gas):

import { createPublicClient, http } from "viem";
import { base } from "viem/chains";

const client = createPublicClient({ chain: base, transport: http() });

// Check who owns a token
const owner = await client.readContract({
  address: "0x8004A169FB4a3325136EB29fA0ceB6D2e539a432",
  abi: [
    {
      inputs: [{ name: "agentId", type: "uint256" }],
      name: "ownerOf",
      outputs: [{ name: "", type: "address" }],
      stateMutability: "view",
      type: "function",
    },
  ],
  functionName: "ownerOf",
  args: [42n],
});

// Read an agent's metadata URI
const uri = await client.readContract({
  address: "0x8004A169FB4a3325136EB29fA0ceB6D2e539a432",
  abi: [
    {
      inputs: [{ name: "tokenId", type: "uint256" }],
      name: "tokenURI",
      outputs: [{ name: "", type: "string" }],
      stateMutability: "view",
      type: "function",
    },
  ],
  functionName: "tokenURI",
  args: [42n],
});

7. Resources

• 8004.org — ERC-8004 protocol
• Base — Base L2 chain
• BaseScan — Base block explorer
• viem — TypeScript Ethereum library

Summary

1. Set up wallet — generate a private key, derive address, store securely.
2. Fund wallet — get ETH on Base (Coinbase, bridge, or transfer). $1 is more than enough.
3. Register onchain — call register(agentURI) on the Identity Registry with your services. Parse the Transfer event for your token ID.
4. Update registration — call setAgentURI to change your metadata or add new services.