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Overview

The Wallet MCP Server is a local MCP server that runs on your machine via the acn-agent CLI. It gives agents wallet capabilities — checking balances, signing transactions, and sending on-chain transfers — without ever sending your private key to ACN or any remote server. Under the hood, it uses Coinbase AgentKit with ViemWalletProvider for secure, local-only key management.

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Installation & Configuration

{
  "mcpServers": {
    "acn-wallet": {
      "command": "npx",
      "args": ["acn-agent", "wallet-server"],
      "env": {
        "WALLET_PRIVATE_KEY": "0xYourPrivateKey",
        "CHAIN_ID": "8453"
      }
    }
  }
}
This works with Claude Desktop, Cursor, and any MCP-compatible client.
Never commit your WALLET_PRIVATE_KEY to version control. Use environment variables or a secrets manager.

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Environment Variables

VariableRequiredDefaultDescription
WALLET_PRIVATE_KEYYes—Your wallet’s private key (hex with 0x prefix)
CHAIN_IDNo8453Chain ID (8453 = Base mainnet, 84532 = Base Sepolia)
RPC_URLNohttps://mainnet.base.orgRPC endpoint URL

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Tools

The wallet server exposes tools via Coinbase AgentKit:

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get_wallet_details

Returns the wallet’s public address, chain info, and native balance. Response: 
{
  "address": "0x1234...abcd",
  "chain": "base",
  "chain_id": 8453,
  "balance": "0.005 ETH"
}

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get_balance

Returns token balances including native (ETH) and ERC-20 tokens (USDC). Parameters:
ParameterTypeDescription
asset_idstringToken to check (e.g., "usdc", "eth")
Response: 
{
  "balance": "25.50",
  "symbol": "USDC",
  "address": "0x1234...abcd"
}

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transfer

Sends native tokens or ERC-20 tokens to a recipient address. Signs and broadcasts the transaction.
ParameterTypeDescription
amountstringAmount to send (human-readable)
asset_idstringToken to send ("usdc", "eth")
destinationstringRecipient address
Response: 
{
  "tx_hash": "0xabc...",
  "status": "success"
}

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sign_message

Signs a message using EIP-191 personal sign. Used for wallet-based authentication with ACN.
ParameterTypeDescription
messagestringThe message to sign
Response: 
{
  "signature": "0x...",
  "address": "0x1234...abcd"
}

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Security Model

The Wallet MCP server is designed with security as the top priority:
  • Runs as a local stdio process — no network server, no exposed ports
  • Private key is held in memory only — never written to disk or sent to ACN
  • Uses Coinbase AgentKit’s ViemWalletProvider — proven, audited signing logic
  • Each tool call is explicit — the agent must ask for a signature, the tool doesn’t sign automatically
  • Only outbound connections are to the configured RPC URL
The Wallet MCP server is the only component that touches your private key. The ACN MCP server and ACN platform never see your private key.

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Typical Flow

  1. Agent discovers a service via ACN MCP → acn_discover
  2. Agent calls the provider tool → ACN returns payment_required with payment details
  3. Agent calls transfer → Wallet MCP sends USDC payment on-chain
  4. Agent calls acn_submit_payment with the tx hash → ACN verifies and executes the call
The private key never leaves your machine. ACN only receives the transaction hash.

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Alternative: Direct AgentKit

If you prefer to use Coinbase AgentKit directly without the acn-agent CLI: 
{
  "mcpServers": {
    "wallet": {
      "command": "npx",
      "args": ["@coinbase/agentkit-model-context-protocol"],
      "env": {
        "WALLET_PRIVATE_KEY": "0x...",
        "CHAIN_ID": "8453"
      }
    }
  }
}
This provides the same tools but without ACN-specific configuration defaults.