MetaMask Agent Wallet Skill

Controls a sandboxed MetaMask wallet for autonomous blockchain transactions with configurable permission guardrails.

Overview

This skill allows AI agents to interact with dapps and execute transactions through a dedicated MetaMask wallet. All operations are subject to user-defined constraints (spend limits, protocol allowlists, approval thresholds).

Security Model: The agent controls a separate wallet in an isolated browser profile. Never use your main wallet.

Setup

1. Install Dependencies

cd metamask-agent-skill
npm install
npx playwright install chromium

2. Create Agent Wallet Profile

npm run setup

This will:

• Create a fresh Chrome profile at ~/.agent-wallet/chrome-profile
• Install MetaMask extension
• Guide you through wallet creation (use a NEW seed phrase)

3. Fund the Wallet

Transfer a small amount to your agent wallet:

• ETH for gas (0.01-0.05 ETH recommended)
• Tokens for operations (start small, e.g., $50 USDC)

4. Configure Permissions

Edit permissions.json to set your constraints:

{
  "constraints": {
    "spendLimit": {
      "daily": "50000000",    // $50 in 6-decimal format
      "perTx": "10000000"     // $10 max per transaction
    },
    "allowedChains": [1, 137, 42161],
    "allowedProtocols": ["0x...uniswap", "0x...1inch"]
  }
}

Available Actions

Connect to Dapp

connect <dapp-url>

Navigates to dapp and connects the agent wallet.

Example: connect https://app.uniswap.org

Execute Swap

swap <amount> <token-in> for <token-out> [on <dex>]

Executes a token swap on an allowed DEX.

Example: swap 0.01 ETH for USDC on uniswap

Send Tokens

send <amount> <token> to <address>

Sends tokens to an address (within spend limits).

Example: send 10 USDC to 0x1234...

Sign Message

sign <message>

Signs an arbitrary message. Use with caution.

Check Balance

balance [token]

Returns wallet balances.

View Transaction History

history [count]

Shows recent agent transactions with outcomes.

Constraints

All operations check against permissions.json before execution:

Constraint	Description
spendLimit.daily	Max USD value per 24h period
spendLimit.perTx	Max USD value per transaction
allowedChains	Whitelisted chain IDs
allowedProtocols	Whitelisted contract addresses
blockedMethods	Forbidden function selectors
requireApproval.above	Threshold requiring user confirmation

Approval Flow

When a transaction exceeds requireApproval.above:

1. Agent pauses execution
2. Transaction details are logged
3. Agent reports: "Transaction requires approval: [details]"
4. User must explicitly approve before agent continues

Safety

• Isolated Profile: Agent uses separate Chrome profile, never your main browser
• Separate Wallet: Agent wallet is completely separate from your main wallet
• Spend Caps: Hard limits prevent runaway spending
• Protocol Allowlist: Only whitelisted contracts can be called
• Full Logging: Every transaction intent and outcome is logged
• Revocation: Set "revoked": true in permissions.json to disable all actions

Logging

All transactions are logged to ~/.agent-wallet/logs/:

{
  "timestamp": 1706900000000,
  "action": "swap",
  "intent": { "to": "0x...", "value": "0", "data": "0x..." },
  "guardResult": { "allowed": true },
  "outcome": "confirmed",
  "txHash": "0x..."
}

Use history command to view recent transactions.

Troubleshooting

"Protocol not allowed"

Add the contract address to allowedProtocols in permissions.json.

"Exceeds daily limit"

Wait 24h or increase spendLimit.daily.

MetaMask popup not detected

Ensure the browser profile path is correct and MetaMask is installed.

Transaction simulation failed

The dapp may be trying to call a blocked method or unsupported chain.

Architecture

src/
├── index.ts          # Main entry point
├── browser.ts        # Playwright browser management
├── wallet.ts         # MetaMask interaction primitives
├── guard.ts          # Permission enforcement
├── logger.ts         # Transaction logging
├── price.ts          # USD price estimation
├── types.ts          # TypeScript types
└── config.ts         # Configuration loading

Integration with Gator

When Gator accounts are available, permissions.json can be replaced with on-chain permission attestations. The guard will validate against Gator's permission registry instead of local config.