# Mint an ERC-8004 Agent NFT on Mantle — Build Guide > **What this is:** Step-by-step guide to giving your AI agent a real on-chain identity by minting an ERC-8004 NFT on Mantle Sepolia testnet. Includes the explainer for what ERC-8004 is, why it matters, and the full mint flow. > > **Build time:** ~15 minutes. > **Cost:** $0 (testnet — free MNT from faucet). > **Skill level:** comfortable with a terminal, copy-pasting commands, and editing a couple of files. --- ## Quick Facts ``` ┌──────────────────────────────────────────────────────────────────────┐ │ │ │ Standard ............... ERC-8004 ("Trustless Agents") │ │ Authored by ............ MetaMask · Ethereum Foundation · │ │ Google · Coinbase │ │ Chain ................. Mantle Sepolia (testnet, free) │ │ Mainnet status ........ Deployed Feb 16, 2026 │ │ What you mint ......... An ERC-721 NFT representing your agent │ │ Cost .................. ~0.0001 test MNT (free from faucet) │ │ Where it shows up ..... 8004scan.io (mainnet) / mantlescan.xyz │ │ │ └──────────────────────────────────────────────────────────────────────┘ ``` --- # Part 1: The Big Picture ## The Problem AI agents are everywhere — marketing agents, trading bots, customer-support bots, the lot. But they all live in silos. There's no standard way to answer: - **Who is this agent?** (no identity) - **Has it done good work before?** (no portable reputation) - **Can I prove it actually did what it claims?** (no validation) - **How do I find it / pay it / talk to it?** (no discovery) The Mantle team calls this the **"visibility crisis."** Agents can call APIs, run code, hold money — but they're invisible to the broader financial system because they have no credentials. ## The Solution: ERC-8004 ``` ┌──────────────────────────────────────────────────────────────────────┐ │ │ │ THREE REGISTRIES │ │ ════════════════ │ │ │ │ 1. IDENTITY REGISTRY │ │ Each agent gets a unique ERC-721 NFT. │ │ The NFT points to a JSON file with name, image, endpoints. │ │ → This is what you'll mint today. │ │ │ │ 2. REPUTATION REGISTRY │ │ Anyone can leave on-chain feedback on your agent. │ │ Your agent's track record is portable across platforms. │ │ │ │ 3. VALIDATION REGISTRY │ │ Cryptographic proof of work completed. │ │ zkML, TEE attestations, stake-secured re-execution. │ │ │ └──────────────────────────────────────────────────────────────────────┘ ``` ## Why Mantle Mantle deployed all three registries on mainnet in February 2026 — they're positioning their L2 as the hub for the "Internet of Agents," especially for real-world assets and DeFi. They were one of the first major L2s to do this. We'll mint on **Mantle Sepolia** (testnet) so it's free. The flow is identical for mainnet. ## How It Fits With Other Standards ``` Your AI Agent │ ┌──────────────┼──────────────┐ │ │ │ ERC-8004 MCP x402 (identity) (tools) (payments) │ A2A (agent-to-agent communication) ``` ERC-8004 gives your agent **identity + reputation**. Combine it with: - **MCP** (Model Context Protocol) → agent uses tools - **x402** → agent gets paid in stablecoins - **A2A** → agent talks to other agents Stack all four and your agent is a full citizen of the agent internet. --- # Part 2: What You'll Have at the End ``` ┌──────────────────────────────────────────────────────────────────────┐ │ │ │ ✓ AGENT NFT OWNERSHIP │ │ An ERC-8004 NFT on Mantle Sepolia, owned by your wallet. │ │ │ │ ✓ CUSTOM METADATA │ │ Your agent's name, description, and image — rendered in any │ │ NFT viewer. │ │ │ │ ✓ SERVICE ENDPOINTS │ │ One or more endpoints: web, A2A, MCP, email, ENS, DID. │ │ │ │ ✓ WALLET BINDING │ │ Your wallet address bound as the verified agentWallet. │ │ │ │ ✓ VERIFICATION & PROOF │ │ Visible on Mantlescan with the transaction hash as proof. │ │ (Mainnet mints show up on 8004scan.io.) │ │ │ └──────────────────────────────────────────────────────────────────────┘ ``` --- # Part 3: The Plan in 5 Steps ``` ┌───────────────────────────────────────────────────────────────┐ │ │ │ STEP 1 Add Mantle Sepolia + claim test MNT │ │ STEP 2 Host the image + write agent.json │ │ STEP 3 Host the agent.json (Pinata or Gist) │ │ STEP 4 Set up Hardhat + run mint script │ │ STEP 5 Verify the agent on Mantlescan │ │ │ │ Total: ~15 min. No contracts to deploy — registries are │ │ already live on Mantle. │ │ │ └───────────────────────────────────────────────────────────────┘ ``` --- # Part 4: Mantle Sepolia Network Info Add this network to your wallet (MetaMask, Rabby, etc.): ``` ┌──────────────────────────────────────────────────────────────────────┐ │ │ │ NETWORK NAME ........... Mantle Sepolia │ │ CHAIN ID ............... 5003 │ │ RPC URL ................ https://rpc.sepolia.mantle.xyz │ │ CURRENCY ............... MNT │ │ EXPLORER ............... https://sepolia.mantlescan.xyz │ │ │ │ ONE-CLICK ADD .......... https://chainlist.org/chain/5003 │ │ │ │ FAUCETS (any one works): │ │ · https://sepolia-faucet.pk910.de │ │ · https://faucet.sepolia.mantle.xyz │ │ · https://app.mantle.xyz/bridge?network=sepolia │ │ │ │ REGISTRY ADDRESSES: │ │ Identity → 0x8004A818BFB912233c491871b3d84c89A494BD9e │ │ Reputation → 0x8004B663056A597Dffe9eCcC1965A193B7388713 │ │ │ └──────────────────────────────────────────────────────────────────────┘ ``` > **Pro tip:** Use the chainlist.org link above — it adds Mantle Sepolia in one click. Faster than typing the RPC manually. --- # Part 5: Step 1 — Host the Agent Image Your agent needs a face. Any image (PNG/JPG/SVG) on any public URL works. **Two easy options:** ``` ┌──────────────────────────────────────────────────────────────────────┐ │ │ │ OPTION A — PINATA (IPFS, recommended for mainnet) │ │ ───────────────────────────────────────────────────── │ │ 1. Sign up at pinata.cloud (free) │ │ 2. Files → Upload → drag your image │ │ 3. Copy the IPFS CID │ │ 4. Use as: ipfs:// OR the gateway URL │ │ │ │ OPTION B — IMGUR (faster, for testing) │ │ ───────────────────────────────────────────── │ │ 1. Go to imgur.com │ │ 2. Drag your image in │ │ 3. Right-click the uploaded image → "Copy image address" │ │ 4. Make sure it ends in .png / .jpg / .gif │ │ │ └──────────────────────────────────────────────────────────────────────┘ ``` **Save the URL** — you'll paste it into `agent.json` in the next step. > **⚠ Gotcha:** If you use Imgur, make sure you get the *direct* image URL (ends in .png/.jpg/.gif), not the page URL (imgur.com/abc123). Right-click the image after upload → "Copy image address." --- # Part 6: Step 2 — Hardhat Project Setup Open a terminal and run this one-shot command to scaffold everything: ```bash # macOS / Linux mkdir ~/Desktop/mint-8004 && cd ~/Desktop/mint-8004 && \ npm init -y && npm pkg set type=module && \ npm install --save-dev hardhat ethers dotenv @nomicfoundation/hardhat-ethers && \ mkdir scripts && touch hardhat.config.js agent.json .env scripts/mint-agent.js && \ code . ``` ```powershell # Windows (PowerShell) cd "$env:USERPROFILE\Desktop"; mkdir mint-8004; cd mint-8004; ` npm init -y; npm pkg set type=module; ` npm install --save-dev hardhat ethers dotenv @nomicfoundation/hardhat-ethers; ` mkdir scripts; ni hardhat.config.js, agent.json, .env, scripts\mint-agent.js; ` code . ``` You should now have a folder like this: ``` mint-8004/ ├── hardhat.config.js ├── agent.json ├── .env ├── package.json ├── scripts/ │ └── mint-agent.js └── node_modules/ ``` ## hardhat.config.js ```javascript import "@nomicfoundation/hardhat-ethers"; import "dotenv/config"; export default { solidity: "0.8.24", networks: { mantleSepolia: { type: "http", url: process.env.RPC, chainId: 5003, accounts: process.env.PK ? [process.env.PK] : [], }, }, }; ``` ## agent.json This is your agent's identity card. Customize every field for your agent: ```json { "type": "https://eips.ethereum.org/EIPS/eip-8004#registration-v1", "name": "Goldwing", "description": "A pixel-art rooster fighter and on-chain agent.", "image": "https://violet-kind-canidae-922.mypinata.cloud/ipfs/YOUR_CID_HERE", "services": [ { "name": "web", "endpoint": "https://yoursite.com" }, { "name": "email", "endpoint": "you@yoursite.com" } ], "x402Support": false, "active": true, "registrations": [], "supportedTrust": ["reputation"] } ``` **Field guide:** | Field | What it is | |-------|------------| | `name` | Your agent's display name | | `description` | One-line description (~200 chars) | | `image` | URL from Step 1 | | `services` | How others reach your agent (web, MCP, A2A, email, ENS, DID) | | `x402Support` | Set `true` if your agent accepts x402 payments | | `supportedTrust` | Which trust mechanism — `reputation`, `validation`, `tee` | ## .env ```bash PK=0xYOUR_PRIVATE_KEY_HERE RPC=https://rpc.sepolia.mantle.xyz AGENT_URI=https://.../agent.json ``` > **⚠ NEVER commit `.env` to GitHub.** Add `.env` to your `.gitignore` immediately. Treat your private key like a password — if leaked, anyone can drain that wallet. > **Use a burner wallet for testing.** Generate a fresh wallet in MetaMask, send it some test MNT, use that private key. Don't use your main wallet's key. --- # Part 7: Step 3 — Host the JSON Same idea as the image. The `agent.json` file needs to live at a public URL. ``` ┌──────────────────────────────────────────────────────────────────────┐ │ │ │ OPTION A — PINATA IPFS │ │ ──────────────────── │ │ pinata.cloud → Files → Upload your agent.json │ │ Copy the file URL → paste into .env as AGENT_URI │ │ │ │ OPTION B — GITHUB GIST │ │ ─────────────────── │ │ 1. gist.github.com → New gist │ │ 2. Filename: agent.json │ │ 3. Paste the JSON │ │ 4. "Create secret gist" │ │ 5. Click "Raw" → copy the URL │ │ 6. Paste into .env as AGENT_URI │ │ │ └──────────────────────────────────────────────────────────────────────┘ ``` > **Note for production:** Use IPFS (Pinata) for mainnet — IPFS URLs are content-addressed and immutable. Gists are fine for testnet but the URL can change if you edit it. --- # Part 8: Step 4 — Mint the Agent Drop this into `scripts/mint-agent.js`: ```javascript import { ethers } from "ethers"; import "dotenv/config"; import fs from "fs"; const REG = "0x8004A818BFB912233c491871b3d84c89A494BD9e"; const ABI = [ "function register(string) external returns (uint256)", "event Registered(uint256 indexed agentId, string agentURI, address indexed owner)" ]; async function main() { // Read agent.json and inline it as base64 data URI const json = fs.readFileSync("./agent.json", "utf8"); const agentURI = "data:application/json;base64," + Buffer.from(json).toString("base64"); // Connect to Mantle Sepolia const provider = new ethers.JsonRpcProvider(process.env.RPC); const wallet = new ethers.Wallet(process.env.PK, provider); const contract = new ethers.Contract(REG, ABI, wallet); console.log("Minting agent NFT..."); const tx = await contract.register(agentURI); console.log("Tx submitted:", tx.hash); const receipt = await tx.wait(); const event = receipt.logs.find( (l) => l.topics[0] === ethers.id("Registered(uint256,string,address)") ); console.log("✅ agentId:", BigInt(event.topics[1]).toString()); console.log("🔗 https://sepolia.mantlescan.xyz/tx/" + tx.hash); } main().catch(console.error); ``` Run it: ```bash npx hardhat run scripts/mint-agent.js --network mantleSepolia ``` You should see something like: ``` Minting agent NFT... Tx submitted: 0xabc123... ✅ agentId: 42 🔗 https://sepolia.mantlescan.xyz/tx/0xabc123... ``` > **Two ways to embed the agent file in the NFT** — this script uses a **base64 data URI** (the JSON lives directly inside the NFT, no external hosting needed). The alternative is using your hosted `AGENT_URI` (the JSON lives at an external URL). Data URI is simpler for testing; hosted URI is better for production because it's editable later via `setAgentURI()`. --- # Part 9: Step 5 — Verify Everything ## On Mantlescan Click the transaction link from the script output. You should see: - Status: **Success** - A `Registered` event with your agentId - Your wallet listed as the owner ## On-chain state checks You can read the contract directly. In Hardhat console: ```bash npx hardhat console --network mantleSepolia ``` ```javascript const reg = await ethers.getContractAt( ["function ownerOf(uint256) view returns (address)", "function tokenURI(uint256) view returns (string)"], "0x8004A818BFB912233c491871b3d84c89A494BD9e" ); await reg.ownerOf(YOUR_AGENT_ID); // → should be your wallet await reg.tokenURI(YOUR_AGENT_ID); // → should be your agentURI ``` ## Metadata check Open your `image` URL in a browser → confirms the image renders. Open your `AGENT_URI` (if hosted) → confirms the JSON loads. ## On 8004scan.io (mainnet only) Once you migrate to Mantle mainnet, your agent appears at: `https://8004scan.io/agents/mantle/` Searchable by wallet address from the homepage. --- # Part 10: Design Decisions & Gotchas ``` ┌──────────────────────────────────────────────────────────────────────┐ │ │ │ WHY MANTLE SEPOLIA (NOT MAINNET) │ │ ───────────────────────────────── │ │ Mainnet costs real MNT and your agent shows up on 8004scan.io │ │ immediately. For learning + iterating: testnet. For real │ │ production agents: mainnet, same flow. │ │ │ │ WHY DATA URI INSTEAD OF HOSTED URL │ │ ────────────────────────────────── │ │ Inlining the JSON as base64 means your agent is fully self- │ │ contained on-chain. No external hosting to maintain. Tradeoff: │ │ you can't easily edit the agent file later. For production, │ │ host on IPFS via Pinata and use the IPFS URL. │ │ │ │ WHY THREE REGISTRIES │ │ ──────────────────── │ │ Identity is what you mint today — a unique ERC-721 NFT. │ │ Reputation comes from interactions over time (others leave │ │ feedback). Validation is for high-stakes work where reputation │ │ alone isn't enough (zkML proofs, TEE attestations). │ │ │ │ WHY ERC-721 INSTEAD OF SOMETHING NEW │ │ ──────────────────────────────────── │ │ Every wallet, marketplace, and indexer already supports ERC-721. │ │ Making agent identities ERC-721 NFTs means they're immediately │ │ discoverable across the entire NFT ecosystem. Smart design. │ │ │ │ WHY THE supportedTrust FIELD │ │ ─────────────────────────── │ │ Lets other agents filter for the trust level they need before │ │ hiring you. A high-stakes financial agent might require │ │ "validation"; a casual agent might accept "reputation." │ │ │ └──────────────────────────────────────────────────────────────────────┘ ``` ## Gotchas ``` ┌────────────────────────────────────────────────────────────────────┐ │ │ │ ✗ Forgot to add `.env` to `.gitignore` │ │ → Your private key is now public if you push to GitHub. │ │ → Use a burner wallet. Never commit .env. │ │ │ │ ✗ Used the wrong Identity Registry address │ │ → Mantle Sepolia uses 0x8004A818BFB9... │ │ → Mainnet uses a different address. Don't mix them. │ │ │ │ ✗ Image URL is the page URL, not the direct image URL │ │ → NFT viewers will show a broken image. │ │ → Right-click → Copy image address. URL must end in .png/.jpg. │ │ │ │ ✗ "Cannot read private key" error │ │ → Make sure PK in .env starts with `0x` │ │ → Make sure there are no quotes around it │ │ │ │ ✗ "Insufficient funds" error │ │ → You need test MNT in your wallet. Use one of the faucets. │ │ → Wait 30 seconds after claiming for it to land. │ │ │ │ ✗ Agent.json doesn't load when opened │ │ → If using Gist, make sure you clicked "Raw" before copying │ │ the URL — the regular Gist URL returns HTML, not JSON. │ │ │ │ ✗ "Cannot find module" when running the script │ │ → Make sure package.json has "type": "module" │ │ → Run `npm install` again from inside the project folder │ │ │ │ ✗ Agent doesn't show up on 8004scan.io │ │ → 8004scan.io is mainnet only. Testnet mints don't appear. │ │ → Verify on sepolia.mantlescan.xyz instead. │ │ │ └────────────────────────────────────────────────────────────────────┘ ``` ## .gitignore Drop this into the project root: ``` node_modules/ .env .netlify/ artifacts/ cache/ ``` --- # Part 11: What This Unlocks Next You now have an AI agent with a real on-chain identity. From here: ``` ┌──────────────────────────────────────────────────────────────────────┐ │ │ │ ADD PAYMENTS (x402) │ │ ──────────────────── │ │ Set x402Support: true and add an x402 payment endpoint to your │ │ services. Now your agent can accept micropayments in USDC. │ │ │ │ ADD TOOLS (MCP) │ │ ───────────────── │ │ Expose an MCP endpoint in your services so other agents can use │ │ your agent as a tool. │ │ │ │ BUILD REPUTATION │ │ ──────────────── │ │ Have clients call `giveFeedback(agentId, score, uri)` on the │ │ Reputation Registry after using your agent. Reputation accrues. │ │ │ │ MOVE TO MAINNET │ │ ───────────────── │ │ Same script, mainnet Identity Registry address, real MNT for gas. │ │ Your agent shows up on 8004scan.io alongside 195,000+ others. │ │ │ │ HIRE OTHER AGENTS │ │ ──────────────── │ │ Browse 8004scan.io for agents with the capabilities you need. │ │ Pay them via x402, verify their work via the Validation Registry. │ │ │ └──────────────────────────────────────────────────────────────────────┘ ``` --- # Appendix A: All Resources ## Core specifications - **ERC-8004 EIP:** https://eips.ethereum.org/EIPS/eip-8004 - **ERC-8004 Contracts (GitHub):** https://github.com/erc-8004/erc-8004-contracts - **ERC-8004 Official site:** https://8004.org ## Network access - **Add Mantle Sepolia (1-click):** https://chainlist.org/chain/5003 - **Mantle Sepolia faucet:** https://faucet.sepolia.mantle.xyz - **Mantle bridge:** https://app.mantle.xyz/bridge?network=sepolia ## Explorers - **Mantle Sepolia (testnet):** https://sepolia.mantlescan.xyz - **Mantle mainnet:** https://mantlescan.xyz - **8004scan (multi-chain mainnet agent explorer):** https://8004scan.io ## Hosting - **Pinata (IPFS):** https://pinata.cloud - **Imgur (quick image hosting):** https://imgur.com - **GitHub Gist:** https://gist.github.com ## Mantle ecosystem - **Mantle ERC-8004 Launch announcement (Feb 2026):** https://www.prnewswire.com/news-releases/mantle-unlocks-autonomous-economy-with-erc-8004-deployment-302688549.html - **Mantle Network:** https://www.mantle.xyz ## Further reading - **ERC-8004 deep-dive (QuickNode):** https://blog.quicknode.com/erc-8004-a-developers-guide-to-trustless-ai-agent-identity/ - **ERC-8004 explainer (BuildBear):** https://www.buildbear.io/blog/erc-8004 ## AlphaStack resources - **Channel:** https://youtube.com/@alphastack - **All build guides:** https://alphastack.fun - **Related video — Claude Routines marketing agent:** /claude-routine-marketing-agent - **Related video — Polymarket Edge Trader:** /polymarket-edge-trader --- # Appendix B: Registry Addresses (Reference) ``` MANTLE SEPOLIA (TESTNET) ──────────────────────── Identity Registry 0x8004A818BFB912233c491871b3d84c89A494BD9e Reputation Registry 0x8004B663056A597Dffe9eCcC1965A193B7388713 MANTLE MAINNET ────────────── Check 8004.org or the ERC-8004 contracts GitHub for current mainnet addresses. They are typically the same pattern but verify before deploying real funds. ``` --- **End of guide.** Drop this into Claude Code and tell it "build this" if you want help with any step. Otherwise just follow the 5 steps in order — 15 minutes start to finish. If you got stuck, leave a comment on the video or hit me up at alphastack.fun. --- *Built by AlphaStack · alphastack.fun · Last updated May 15, 2026*