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

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

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

Development

Requires Deno v2.0+.

# Install dependencies
deno install
cd web && deno install && cd ..

# Run MCP server in dev mode
deno task dev

# Run web UI dev server (separate terminal)
deno task dev:web

# Run tests
deno task test

# Build web UI
deno task build:web

# Build for npm
deno task build:npm

# Format code
deno task fmt

# Lint code
deno task lint

Project Structure

Developed with Deno, published to npm via dnt. Source in src/ uses
node: builtins (no Deno-specific APIs) so the npm bundle runs under Node.js.

deno.jsonc              # Deno config + npm package metadata (single source of truth for version)
server.json             # MCP registry manifest (read by LobeHub etc. from git)
scripts/build-npm.ts    # dnt build: reads deno.jsonc, transforms src/ → npm/
├── src/                # Server source (TypeScript, runs under both Deno and Node)
│   ├── index.ts        # CLI entry point
│   ├── mcp-server.ts   # MCP tool definitions
│   ├── http-server.ts  # Lazy-started HTTP server for browser approval UI
│   ├── wallet-signer.ts # Core signing orchestration
│   ├── pending-store.ts # Promise-based request tracking
│   ├── schemas.ts      # Zod schemas for MCP tool inputs
│   ├── transport.ts    # viem custom transport
│   ├── viem-account.ts # viem local account adapter
│   ├── mod.ts          # Library export (npm: "mcp-wallet-signer")
│   ├── wallet-only.ts  # Library export (npm: "mcp-wallet-signer/wallet-only")
│   └── version.ts      # Reads version from package.json at runtime
├── web/                # Svelte UI (wallet approval pages)
│   └── src/
│       ├── App.svelte
│       └── components/ # ConnectWallet, TransactionSigner, MessageSigner
├── tests/
│   ├── *.test.ts       # Unit tests
│   ├── e2e/            # E2E tests (HTTP API)
│   └── e2e-browser/    # E2E tests (Playwright, real browser wallet)
└── npm/                # Generated — dnt output + built web assets

Build pipeline

deno task build:npm runs scripts/build-npm.ts which:

1. Transforms src/ to ESM JavaScript via dnt → npm/esm/
2. Generates npm/package.json from metadata in deno.jsonc
3. Builds the Svelte web UI (web/ → web/dist/)
4. Copies web assets into npm/web/

Dev workflow

deno task dev        # Run MCP server directly with Deno
deno task dev:web    # Vite dev server for web UI (separate terminal)
deno task test       # Unit + E2E API tests
deno task check      # Type check + lint + format check

License

MIT