Geode local signer

Signs Geode blockchain transactions on your own machine, for AI agents that use the Geode MCP server.

The Geode MCP server lets an agent read from and write to Geode's apps (marketplace, social, messaging, surveys and more). The server never holds your keys. When your agent wants to write, the server prepares an unsigned transaction, and this signer:

1. decodes it independently, without trusting anything the server says about it: which chain, which app contract, which action, which arguments, how much GEODE;

2. refuses anything that isn't an allowed Geode action matching what it claims to be;

3. only then signs it, with a key that never leaves your machine.

It runs next to your agent as a local MCP server (stdio). No key, password or recovery phrase is ever returned by any of its tools, so none can end up in a model's context.

Using the Geode MCP server is governed by Section 10 of the Geode Terms of Use: https://geodechain.com/tos/.

Install

You need Node.js 22 or newer.

Add the signer to your agent's MCP configuration, next to the Geode server. Use full paths, and pin the version:

{
  "mcpServers": {
    "geode": { "url": "https://mcp.geodeapps.com/mcp" },
    "geode-signer": {
      "command": "npx",
      "args": [
        "-y", "@geodechain/local-signer@0.1.0",
        "--dir", "/Users/you/geode-keys",
        "--server", "https://mcp.geodeapps.com/mcp",
        "--per-tx-geode", "50",
        "--per-day-geode", "200"
      ]
    }
  }
}

Create the keys folder first, readable only by you:

mkdir -p ~/geode-keys && chmod 700 ~/geode-keys

From source

git clone https://github.com/geodechain/geode-local-signer.git
cd geode-local-signer
git checkout v0.1.0
npm ci
npm test
npm run build            # → dist/geode-local-signer.mjs

Then use "command": "node", "args": ["/full/path/to/dist/geode-local-signer.mjs", "--dir", …].

Related MCP server: chain-signer

Options

Set --per-tx-geode and --per-day-geode to what your agent actually needs. They are enforced here, on your machine, whatever any server says.

Tools

Existing accounts: put the polkadot.js JSON keystore (<address>.json) in --dir, with a file <name>-password.txt containing only its password. Keep the files at 600.

What it refuses to sign

• a transaction for another chain, or one that never expires;

• anything other than a call to one of Geode's eight app contracts or a keep-alive GEODE transfer (so it can never empty your account);

• an action that isn't in its tool list, or a payload that doesn't match the action it claims;

• GEODE attached to an action that doesn't take payment;

• more GEODE than --per-tx-geode or --per-day-geode allow, or a storage deposit above --max-storage-deposit-geode;

• a transfer whose recipient and amount don't match what your agent stated separately (expect).

When a refusal might mean the server has tools newer than this signer knows, the message tells you how to update.

Keeping it genuine

• Pin an exact version in your configuration, as above, and update deliberately.

• Releases are built only by this repository's GitHub Actions workflow, with npm provenance linking each version to the commit that built it (check with npm audit signatures). Each release needs two separate human approvals: one in GitHub, then one on npm with two-factor authentication.

• The published file is not minified, so you can read it and compare it with the source.

• It has no runtime dependencies: installing it downloads this one file and nothing else.

Security

See SECURITY.md. Report vulnerabilities privately to support@geodechain.com.

License

Apache License 2.0. Copyright 2026 The Geode Foundation Inc. See LICENSE and NOTICE.