Justhandled Agent Client MCP Server

JustHandled Agent Client

A guarded CLI, JavaScript client, and local MCP server for the JustHandled Agent Utility Gateway. The package exposes twenty deterministic preflights and evidence products. Nineteen individual checks cost $0.05 USDC; the consolidated six-check Agent Run Evidence Pack costs $0.25. Every paid call returns a versioned evidence receipt.

The client fails closed before signing. It accepts only the pinned JustHandled gateway, Base mainnet, canonical Base USDC, the exact per-product price, and the published merchant receiver. Customer inputs are not persisted by the gateway.

Inspect without a wallet

npx --package @justhandledlabs/agent-client justhandled-agent catalog
npx --package @justhandledlabs/agent-client justhandled-agent preview filename-portability-preflight --json '{"paths":["CON.txt"]}'
npx --package @justhandledlabs/agent-client justhandled-agent preview agent-run-evidence-pack --file agent-run-evidence-pack.sample.json

Preview performs an unpaid request and validates the returned x402 terms. It does not sign or spend.

The catalog includes API-response contract drift, webhook contract and replay, and policy-change evidence products. Packaged example inputs are available in examples/.

Machine-readable products, exact payment terms, and free deterministic fixtures are available from the gateway's product catalog, OpenAPI document, and sandbox index.

Execute one paid utility

Use a dedicated low-balance Base wallet. Never provide a primary wallet key.

export JH_EVM_PRIVATE_KEY=0x...
npx --package @justhandledlabs/agent-client justhandled-agent call filename-portability-preflight --json '{"paths":["CON.txt"]}'

PowerShell:

$env:JH_EVM_PRIVATE_KEY = "0x..."
npx.cmd --package @justhandledlabs/agent-client justhandled-agent call filename-portability-preflight --json '{"paths":["CON.txt"]}'

MCP configuration

{
  "mcpServers": {
    "justhandled": {
      "command": "npx",
      "args": ["-y", "@justhandledlabs/agent-client"],
      "env": {
        "JH_EVM_PRIVATE_KEY": "0xDEDICATED_LOW_BALANCE_WALLET_KEY"
      }
    }
  }
}

The MCP server exposes a free catalog tool plus one paid tool per gateway utility. Missing wallet configuration produces an error instead of a payment attempt.

The package declares the official MCP Registry identity io.github.justhandledlabs/agent-gateway. Registry identity is discovery metadata only: installing or listing the server does not spend funds, and paid execution still requires a dedicated wallet plus the client's exact-term checks.

Security model

• Price, chain, asset, receiver, and gateway origin are pinned in code.
• The Agent Run Evidence Pack's 250,000-base-unit price is pinned separately from 50,000-base-unit individual checks.
• Every execution starts with an unpaid 402 preview.
• A mismatched term aborts before signing.
• The package never prints the private key.
• The gateway does not persist raw inputs or results.
• Treat all crypto transfers as irreversible and fund only a dedicated wallet.

Development

npm install
npm run check

The gateway implementation is intentionally not included in this client repository.