Non-custodial MCP server that routes blockchain transactions to your browser
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
| Tool | Description | Browser Required |
|---|---|---|
connect_wallet |
Connect wallet, return address | Yes |
send_transaction |
Send ETH/tokens, call contracts | Yes |
sign_message |
Sign arbitrary message (personal_sign) | Yes |
sign_typed_data |
Sign EIP-712 typed data | Yes |
get_balance |
Read ETH balance (via RPC) | No |
How It Works
- Agent calls an MCP tool (e.g.,
send_transaction) - Server opens browser to a local signing page
- User connects wallet and approves the action
- 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):
| Variable | Description | Default |
|---|---|---|
EVM_MCP_PORT |
HTTP server port | 3847 |
EVM_MCP_DEFAULT_CHAIN |
Default chain ID | 1 |
Packages
This is a monorepo with two packages:
| Package | Description |
|---|---|
| `browser-evm-signer` | Standalone library — sign EVM transactions via browser wallet, no MCP dependency |
| `mcp-wallet-signer` | MCP server — exposes browser-evm-signer as MCP tools for AI agents |
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
Tools (5)
connect_walletConnect wallet and return the user's addresssend_transactionSend ETH/tokens or call smart contractssign_messageSign an arbitrary message using personal_signsign_typed_dataSign EIP-712 typed dataget_balanceRead ETH balance via RPCEnvironment Variables
EVM_MCP_PORTHTTP server portEVM_MCP_DEFAULT_CHAINDefault chain IDConfiguration
{"mcpServers": {"evm-wallet": {"command": "npx", "args": ["-y", "mcp-wallet-signer"]}}}