usbtmc_send · USBTMC MCP Server MCP: Risk & Policy

WHAT IT DOES

What usbtmc_send does on USBTMC MCP Server

AI agents invoke usbtmc_send to trigger actions in USBTMC MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why usbtmc_send needs a policy

The tool name 'usbtmc_send' on a USBTMC/SCPI instrument control server almost certainly sends SCPI commands to test and measurement hardware. Sending arbitrary SCPI commands to lab instruments can trigger physical operations (e.g., high-voltage outputs, relay switching, waveform generation), making this an Execute-level action.

From the tool's definition Tool name 'usbtmc_send' on a server that 'Enables controlling multiple USBTMC devices simultaneously using SCPI commands'. Sibling tool 'usbtmc_query' suggests send is the write/command counterpart.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

usbtmc_send Rate-limited

usbtmc_send stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "usbtmc_send": {
      "limits": [
        {
          "counter": "usbtmc_send_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches USBTMC MCP Server, so you can run agents against it safely.

FAQ

Questions about usbtmc_send

What does the usbtmc_send tool do? +

usbtmc_send. It is categorised as a Execute tool in the USBTMC MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on usbtmc_send? +

Register the USBTMC MCP Server MCP server in PolicyLayer and add a rule for usbtmc_send: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches USBTMC MCP Server. Nothing to install.

What risk level is usbtmc_send? +

usbtmc_send is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit usbtmc_send? +

Yes. Add a rate_limit block to the usbtmc_send rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block usbtmc_send completely? +

Set action: deny in the PolicyLayer policy for usbtmc_send. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides usbtmc_send? +

usbtmc_send is provided by the USBTMC MCP Server MCP server (naonaome/usbtmc-lite-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.