MCP Wallet Signer (io.github.nikicat/mcp-wallet-signer)

This MCP server routes EVM transactions to browser wallets (e.g., MetaMask) for signing via EIP-6963. It is implemented as io.github.nikicat/mcp-wallet-signer and is part of the Model Context Protocol tooling ecosystem, targeting non-custodial browser-based signing flows.

🛠️ Key Features

EVM transaction routing to browser wallets (MetaMask, etc.)
Signing flow based on EIP-6963
Topics include MCP, Ethereum, web3, and TypeScript

🚀 Use Cases

Request EVM transaction signatures through a browser wallet integration
Support developer setups that use EIP-6963 for wallet discovery/interaction
Integrate wallet signing within MCP-based workflows

⚡ Developer Benefits

Non-custodial signing using browser wallets
EIP-6963-based browser-wallet signing workflow
TypeScript-oriented server package available via npm (MIT license)

⚠️ Limitations

Marked as superseded by browser-web3-signer (reimplemented in Rust, with a CLI and Rust/TypeScript/Go libraries); it “still work” but is not the current replacement.

mcp-wallet-signer

WARNING

Superseded by browser-web3-signer — the same browser-wallet signing flow, reimplemented in Rust with a CLI plus Rust/TypeScript/Go libraries. Everything published from this repo is now a thin compatibility shim over it, so existing installs keep working; new code should use browser-web3-signer directly.

Your private keys never leave your browser. Every transaction requires explicit approval in your own wallet (MetaMask, Rabby, TronLink, …).

Most blockchain tooling wants a private key in a config file — full, unsupervised access to your funds. These packages route each request to the browser wallet you already use, so you review and approve it like any other dapp interaction.

Packages

Package	What it is now
`mcp-wallet-signer`	MCP stdio server: four signing tools over `browser-web3-signer`
`browser-evm-signer`	The old `WalletSigner` EVM library API, re-backed by the Rust bridge
`browser-tron-signer`	The same for TRON (TronLink, TRC-20, contract deploys)

All three spawn browser-web3-signer serve, which owns the localhost bridge, the approval page and the browser tab. The binary for your platform is installed as a dependency; nothing else to set up.

MCP server

bash

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

Or, for Claude Desktop / Cursor / Windsurf and any other stdio MCP client:

json

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

Tool	Description
`connect_wallet`	Connect a wallet, return the address
`send_transaction`	Send value or call a contract, return the tx hash
`sign_message`	`personal_sign` a message, return the signature
`sign_typed_data`	Sign EIP-712 typed data, return the signature

EVM_MCP_DEFAULT_CHAIN sets the chain id used when a call omits one (default: 1).

Libraries

import { WalletSigner } from "browser-evm-signer";

const signer = new WalletSigner({ defaultChainId: 8453 });
const { address } = await signer.connectWallet();
const { txHash } = await signer.sendTransaction({ to: "0x…", value: "1000000000000000000" });

What changed in the shims

Gone: PendingStore, pendingStore, createHttpServer, startTestServer, buildConnectUrl, buildSignUrl, openBrowser — the in-process HTTP bridge they drove no longer exists.
approvalUrl is now the bridge's base URL. The bridge opens the approval page itself and does not hand the per-request URL back.
port (the constructor option) is ignored: the bridge binds its own free port. getPort() / DEFAULT_PORT still resolve, for source compatibility.
MCP: the balance tools (get_balance, get_token_balance) and the TRON tools are gone from the MCP server. Balances never needed a wallet — any RPC-reading MCP server or cast call does them without an approval prompt — and TRON signing is a CLI away. WalletSigner.getBalance and .getTokenBalance are untouched in both libraries.
Deprecated on npm and JSR. browser-evm-signer@0.3.0 never worked at all: its exports pointed at ./esm/mod.js while the tarball shipped ./esm/browser-evm-signer/src/mod.js, which took mcp-wallet-signer@0.6.0 down with it (#2).

The pre-shim Deno implementation — the in-process bridge, the Svelte approval UI, the wallet-signer-core package — is in the history, up to commit 636fd3b.

Development

bash

npm install
npm test     # builds, then runs each package's tests against a fake bridge

Releases are per package: tag <package>@<version> and publish a GitHub release.

License

MIT

EVM Wallet Signer