MCP Wallet Signer MCP Server

MCP Wallet Signer

Your private keys never leave your browser. Every transaction requires explicit user approval in your wallet.

Most blockchain MCPs require you to paste a private key into a config file — giving the AI agent full, unsupervised access to your funds. MCP Wallet Signer takes a different approach: it routes every transaction to your actual browser wallet (MetaMask, Rabby, etc.) via EIP-6963, so you review and approve each action just like any other dapp interaction. No keys in config files, no risk of silent transactions.

Compatible With

Works with any MCP-compatible client via stdio transport.

Installation

Claude Code CLI

claude mcp add evm-wallet -- npx -y mcp-wallet-signer

Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "evm-wallet": {
      "command": "npx",
      "args": ["-y", "mcp-wallet-signer"]
    }
  }
}

Run directly

npx -y mcp-wallet-signer
pnpx mcp-wallet-signer
bunx mcp-wallet-signer

MCP Tools

How It Works

1. Agent calls an MCP tool (e.g., send_transaction)
2. Server opens browser to a local signing page
3. User connects wallet and approves the action
4. Result (address, tx hash, signature) returned to agent

Connect Wallet	Send Transaction	Sign Message

Supported Chains

Built-in RPC URLs for:

• Ethereum (1)
• Sepolia (11155111)
• Polygon (137)
• Arbitrum One (42161)
• Optimism (10)
• Base (8453)
• Avalanche (43114)
• BNB Smart Chain (56)

Configuration

Environment variables (optional):

Packages

This is a monorepo with two packages:

Use browser-evm-signer directly if you want browser-based signing in your own Node.js/Deno app without MCP.

Development

Requires Deno v2.0+.

# Install all dependencies
deno task install:all

# Type check + lint + format check (both packages)
deno task check:all

# Run tests
deno task test:all

# Build both npm packages
deno task build:all

# Format code
deno task fmt

Project Structure

packages/
├── browser-evm-signer/     # Standalone signing library (npm: browser-evm-signer)
│   ├── src/                 # Library source
│   ├── web/                 # Svelte approval UI
│   ├── tests/               # Unit, e2e, and browser tests
│   └── scripts/build-npm.ts
│
└── mcp-wallet-signer/       # MCP server layer (npm: mcp-wallet-signer)
    ├── src/                  # MCP tool definitions + CLI entry
    └── scripts/build-npm.ts