serial_send_bytes · MCP Remote Access MCP: Risk & Policy

WHAT IT DOES

What serial_send_bytes does on MCP Remote Access

AI agents invoke serial_send_bytes to trigger actions in MCP Remote Access. 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 serial_send_bytes needs a policy

This tool sends raw binary data directly to a serial port connected to embedded/IoT devices. Sending arbitrary binary data to hardware can trigger commands, change device state, flash firmware, or cause unrecoverable hardware behavior. It is an active operation with external effects on physical devices, making it Execute with high severity due to potential for hardware damage or unintended device control.

From the tool's definition Send raw binary bytes to a serial port (no UTF-8 encoding, no line

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

serial_send_bytes Rate-limited

serial_send_bytes 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": {
    "serial_send_bytes": {
      "limits": [
        {
          "counter": "serial_send_bytes_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 MCP Remote Access, so you can run agents against it safely.

FAQ

Questions about serial_send_bytes

What does the serial_send_bytes tool do? +

Send raw binary bytes to a serial port (no UTF-8 encoding, no line. It is categorised as a Execute tool in the MCP Remote Access MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on serial_send_bytes? +

Register the MCP Remote Access MCP server in PolicyLayer and add a rule for serial_send_bytes: 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 MCP Remote Access. Nothing to install.

What risk level is serial_send_bytes? +

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

Can I rate-limit serial_send_bytes? +

Yes. Add a rate_limit block to the serial_send_bytes 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 serial_send_bytes completely? +

Set action: deny in the PolicyLayer policy for serial_send_bytes. 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 serial_send_bytes? +

serial_send_bytes is provided by the MCP Remote Access MCP server (rfingadam/mcp-remote-access). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.