metamask - SKILL.md Agent Skill

name: metamask

description: Work with MetaMask wallet - add custom networks, import ERC-20 tokens, manage permissions, configure gas settings, and integrate with dApps.

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MetaMask Wallet

Installation

Chrome: https://chrome.google.com/webstore/detail/metamask/nkbihfbeogaeaoehlefnkodbefgpgknn
Firefox: https://addons.mozilla.org/firefox/addon/ether-metamask/
Mobile: iOS App Store / Google Play
Flask (dev): https://metamask.io/flask/

Add Popular Networks

Settings → Networks → Add Network

Polygon:


Network: Polygon Mainnet

RPC: https://polygon-rpc.com

Chain ID: 137

Symbol: MATIC

Explorer: https://polygonscan.com

Arbitrum:


Network: Arbitrum One

RPC: https://arb1.arbitrum.io/rpc

Chain ID: 42161

Symbol: ETH

Explorer: https://arbiscan.io

Optimism:


Network: Optimism

RPC: https://mainnet.optimism.io

Chain ID: 10

Symbol: ETH

Explorer: https://optimistic.etherscan.io

Base:


Network: Base

RPC: https://mainnet.base.org

Chain ID: 8453

Symbol: ETH

Explorer: https://basescan.org

BSC:


Network: BNB Smart Chain

RPC: https://bsc-dataseed.binance.org

Chain ID: 56

Symbol: BNB

Explorer: https://bscscan.com

Avalanche:


Network: Avalanche C-Chain

RPC: https://api.avax.network/ext/bc/C/rpc

Chain ID: 43114

Symbol: AVAX

Explorer: https://snowtrace.io

Import ERC-20 Token

Assets → Import Token → Custom Token

Common tokens (Ethereum):


USDC: 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48

USDT: 0xdAC17F958D2ee523a2206206994597C13D831ec7

DAI: 0x6B175474E89094C44Da98b954EescdeCB5BE3830

WETH: 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2

LINK: 0x514910771AF9Ca656af840dff83E8264EcF986CA

UNI: 0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984

Check Balance (CLI)

ETH balance:


cast balance YOUR_ADDRESS --ether --rpc-url https://eth.llamarpc.com

Token balance:


cast call 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 \

  "balanceOf(address)(uint256)" YOUR_ADDRESS \

  --rpc-url https://eth.llamarpc.com

ENS Names

Resolve ENS:


cast resolve-name vitalik.eth --rpc-url https://eth.llamarpc.com

Reverse lookup:


cast lookup-address YOUR_ADDRESS --rpc-url https://eth.llamarpc.com

Gas Settings

Settings → Advanced → Advanced Gas Controls

Check current gas:


cast gas-price --rpc-url https://eth.llamarpc.com | xargs -I {} cast --to-unit {} gwei

Transaction History

Via Etherscan:


https://etherscan.io/address/YOUR_ADDRESS

Via CLI:


cast etherscan-source YOUR_ADDRESS --etherscan-api-key YOUR_KEY

Connected Sites

Settings → Connected Sites → Manage permissions

Account Management

Create account: Account menu → Create Account

Import: Account menu → Import Account

Hardware Wallet

Connect Ledger/Trezor
Account menu → Connect Hardware Wallet
Select device and address

Custom Nonce

Settings → Advanced → Customize transaction nonce

Get current nonce:


cast nonce YOUR_ADDRESS --rpc-url https://eth.llamarpc.com

Speed Up / Cancel Transaction

Pending tx → Speed Up or Cancel

Replace with CLI:


# Check pending nonce

cast nonce YOUR_ADDRESS --rpc-url https://eth.llamarpc.com

Export Account

Account menu → Account details → Export

Network RPC Endpoints

| Network | Free RPC |

|---------|----------|

| Ethereum | https://eth.llamarpc.com |

| Polygon | https://polygon-rpc.com |

| Arbitrum | https://arb1.arbitrum.io/rpc |

| Optimism | https://mainnet.optimism.io |

| Base | https://mainnet.base.org |

| BSC | https://bsc-dataseed.binance.org |

Troubleshooting

Stuck transaction:


# Get pending nonce

cast nonce YOUR_ADDRESS --pending --rpc-url https://eth.llamarpc.com

Then send 0 ETH to yourself with same nonce + higher gas

Wrong token balance:

Assets → Refresh list, or reimport token

Network not connecting:

Settings → Networks → Edit RPC URL

Reset account:

Settings → Advanced → Clear activity tab data

MetaMask Snaps

Extend functionality with Snaps:

Settings → Snaps → Browse Snaps

Popular snaps:

Transaction Insights
Account Management
Interoperability

Mobile Sync

Mobile: Settings → Sync with Extension
Scan QR code from extension
Or use same recovery phrase

Security Tips

Never share recovery phrase
Verify URLs before connecting
Review permissions before approving
Use hardware wallet for large amounts
Enable phishing detection

Notes

MetaMask is EVM-only (Ethereum and compatible chains)
Default network is Ethereum mainnet
Supports EIP-1559 transactions
Built-in swap via aggregators
Mobile has built-in browser