Mark: agent escrow MCP server

Mark: escrow for AI agents

Let your agent pay another agent, and get paid, without trusting it. Mark is a CLI and MCP server for non-custodial 2-of-3 Bitcoin escrow. Two agents sign the terms. The buyer funds over Lightning, the seller delivers and is paid over Lightning, and a neutral arbiter key only matters if they disagree or one goes silent. No accounts and no custody: each agent holds its own key, and every command prints JSON that agents can act on.

Proof: a real agent-to-agent deal on Bitcoin mainnet ran from create to payout in about 9 minutes. Production deal 6930c46a: 5,000 sats, 330 sats platform fee, 4,634 sats delivered to the seller over Lightning.

Quickstart

npx -y github:yuvlero/mark init                 # optional: any command auto-creates the key on first run
npx -y github:yuvlero/mark pubkey               # share with the counterparty
npx -y github:yuvlero/mark escrow limits --sats 5000
npx -y github:yuvlero/mark escrow create --role buyer --counterparty <pubkey> --sats 5000 --deadline 86400 \
  --title "Logo design" --description "3 concepts" --acceptance "SVG included"
# counterparty: escrow invites -> show <id> -> accept <id>; buyer: fund <id>; seller: evidence --file, approve --payout-lnaddr
npx -y github:yuvlero/mark mcp                  # or run it as an MCP stdio server

Your key is created automatically the first time any command (including mark mcp) needs it, in ~/.mark// (never in the package install dir, so it survives restarts and updates). An existing key is never overwritten. Back up that folder (or run mark backup in a terminal): deleting it loses this identity and access to open deals.

Add --network mutinynet to test without real money. The whole flow is in the agent quickstart; wrappers for skills, LangChain and CrewAI are in examples/.

How it works

Mark is a command-line tool and MCP server. It lets an AI agent buy or sell something from another agent through a non-custodial 2-of-3 escrow on Arkade (Bitcoin), with Lightning in and Lightning out through Satora swaps.

• Three keys: buyer, seller, and the escrow service's arbiter. Any payout needs 2 of the 3 signatures. The service holds only the arbiter key, so it can never move funds alone.
• Happy path: buyer and seller sign the payout together. The arbiter only signs to settle a timeout refund, an automatic rule, or a ruled dispute.
• agent-escrow is the hosted escrow service (arbiter plus coordination API). Mark talks to it over plain HTTPS; the public API is in docs/escrow-api.md.
• Your key never leaves Mark. Before signing, Mark checks locally that the transaction pays exactly the payee amount to the agreed destination plus the published platform fee, and nothing else.

1. Install

Requirements: Node.js ≥ 22.12 (the Arkade SDK's requirement; engines says so) and npm. Linux or macOS. No npm link, no global or root writes, and no native addons. The dependency tree is pinned by npm-shrinkwrap.json and is pure JavaScript, so nothing needs install scripts (npm 11 safe).

Pick one:

# a) npx, nothing kept on PATH (builds on first run, then cached). Once published to npm: npx -y @yuvlero/mark
npx -y github:yuvlero/mark escrow limits

# b) a local clone
git clone https://github.com/yuvlero/mark.git && cd mark
npm ci                       # installs and builds dist/ (prepare step)
node dist/src/cli.js         # prints usage; alias mark="node $PWD/dist/src/cli.js"
npm test                     # optional; offline, mocks the server

# c) a per-user prefix (no sudo, no -g: npm's -g breaks git-dep builds)
npm install --prefix ~/.local/mark github:yuvlero/mark && ~/.local/mark/node_modules/.bin/mark

Below, mark means any of these.

2. Configure the escrow URL

Shortened. The full README is on GitHub.