@arbiterlabs/mcp

@arbiterlabs/mcp

Judgment tools for any MCP-capable agent — Claude Code, Claude Desktop, OpenClaw, or your own host.

Lets a model check whether an action is safe before taking it, rather than finding out afterwards.

Setup

// claude_desktop_config.json, or .mcp.json
{
  "mcpServers": {
    "arbiter": {
      "command": "npx",
      "args": ["-y", "@arbiterlabs/mcp"],
      "env": {
        "ARBITER_URL": "https://arbiter-hs23.onrender.com",
        "ARBITER_PRIVATE_KEY": "base64-64-byte-algorand-key",
        "ARBITER_MAX_SPEND_USD": "10"
      }
    }
  }
}

Tools

Tool	Does	Cost
judge_transaction	Is this transaction safe to sign?	$0.002
judge_counterparty	Is this address who I think it is, and can it receive?	$0.01
judge_human	What would a person say about this?	$0.25
retrieve_human_verdict	Collect a human answer already paid for	free
arbiter_budget	How much has been spent this session	free

Verdicts come back as readable text with the decision first and every finding explained, because that text is what the model reasons over.

Configuration

Variable	Default
ARBITER_URL	http://localhost:4021	Deployment to call
ARBITER_PRIVATE_KEY	—	Base64 Algorand key used to pay
ARBITER_MAX_SPEND_USD	25	Lifetime cap for this process
ARBITER_MAX_PRICE_PER_CALL	1.00	Per-call cap

Paying

Calls are settled per request in USDC on Algorand over x402. There is no API key and no account — payment is the authentication.

Your payer account needs USDC and must be opted in to the USDC asset. On Algorand a transfer to an account that has not opted in is rejected outright, so an un-opted-in payer cannot pay at all. Fees are sponsored by the facilitator, so the payer does not need ALGO.

Route	Price
Transaction verdict	$0.002
Counterparty verdict	$0.01
Human judgment	$0.25

Full documentation: https://arbiter-hs23.onrender.com/docs

Licence

MIT