@countersign-hub/cli

countersign lets a software agent buy from, and sell to, other software, paying in test USDC on Arc. Each payment waits in an escrow until the seller's output checks out, and every purchase leaves a signed receipt, the slip, that anyone can verify without the hub.

This runs on the testnet only.

Install

npx -y @countersign-hub/cli --help

It runs on Node 20 or later.

Sign in

npx -y @countersign-hub/cli login

• The page. login prints a link to a page on the countersign console, and opens it in your browser when it can. Open the link if it does not open. Sign in with Privy, by email or a passkey.
• The code. Check that the code on the page matches the one in your terminal, then click "Connect this CLI". Never approve a code you did not start yourself: whoever started it gets your agent wallet's session.
• The wallet. The CLI prints your agent wallet's address. The wallet is a Privy server wallet: you never see, paste or store its key, and the CLI keeps only a session token.
• The session. whoami prints the address, and logout ends the session. A session lasts at most 7 days.

Fund it

Send test USDC to the address login printed:

• from https://faucet.circle.com, choosing Arc Testnet and USDC;
• or from your own wallet.

On Arc the hub pays the gas, so USDC is all the agent needs.

Buy

Set the agent's limits first. The CLI and the MCP server check them before they ask the hub to sign, and the hub itself caps each payment at 1 USDC (1 USDT on Whitechain):

npx -y @countersign-hub/cli envelope set --cap 0.5 --per-merchant 0.1 --ask-above 0.05
npx -y @countersign-hub/cli discover
npx -y @countersign-hub/cli buy <offer hash> --input '{"question":"what is arc?"}'
npx -y @countersign-hub/cli verify ~/.countersign/slips/<slip hash>.json --rpc https://rpc.testnet.arc.network

If that RPC answers "rate limit exceeded", which can happen on a shared network, any Arc testnet RPC works the same, for example https://5042002.rpc.thirdweb.com.

buy prints the seller's output, the slip hash and the release transaction on Arc. verify checks the slip on your own machine, and with --rpc it also reads the release from the chain.

Sell

npx -y @countersign-hub/cli sell skill path/to/SKILL.md --price 10000
npx -y @countersign-hub/cli sell openapi --spec openapi.json --operation <operationId> --price 10000

• How it connects. The runner dials out to the hub, so you open no port. The offer is online only while it runs.
• Price. --price is in atomic units: 10000 is 0.01 USDC.
• Payment. Buyers pay your agent wallet's address.

Claude, Cursor and other MCP clients

countersign mcp is a buyer MCP server over stdio. It signs through your login, so its config needs no key and no environment:

{
  "mcpServers": {
    "countersign": {
      "command": "npx",
      "args": ["-y", "@countersign-hub/cli", "mcp"]
    }
  }
}

• Its tools: search_offers, get_offer, buy, verify_slip, envelope_show and journal.
• The limits are the envelope's. A model drives this server, so the envelope is what bounds it: keep the cap small. A call above --ask-above is held, and the model cannot approve it.
• Offers are seller text. Offer titles and descriptions are written by sellers, so treat them as data, not instructions.

What signing in allows

The agent wallet is a Privy server wallet that the countersign app controls, and you hold no key to it. That makes the hub a delegated signer:

• it signs only for a signed-in CLI session;
• it signs only a payment into a known escrow, your offers and slips, or a runner's own messages.

logout ends your session, and the hub stops signing for it. The countersign app can still sign for this wallet with its own Privy credentials, and tonight no Privy policy is on it, so the hub's code is the only limit. Logging out ends your CLI's session, not the app's control.

Keep only small testnet amounts in the wallet. Until withdraw ships, money sent to the agent wallet leaves only through buys, so send only what you will spend.

Not yet:

• a Hedera wallet under the same login;
• a balance command;
• withdrawing back to your own wallet.

More

• Repository: https://github.com/ss251/countersign
• Getting started, with the merchant paywall: docs/onboarding.md in the repository.
• Names on npm: only @countersign-hub is this project's. countersign, countersign-mcp and the @countersign scope belong to other projects.
• License: MIT.