{
  "jsonrpc": "2.0",
  "id": 6,
  "method": "tools/call",
  "params": {
    "name": "start_rail_run",
    "arguments": {
      "rail_key": "packetops",
      "environment": "sandbox",
      "idempotency_key": "mcp-run-001",
      "payment_reference": "sandbox_payment_reference",
      "callback_url": "https://example.com/wever-callback"
    }
  }
}