open_uart · Buspirate MCP: Risk & Policy

WHAT IT DOES

What open_uart does on Buspirate

AI agents use open_uart to create or update resources in Buspirate — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Buspirate environment.

WHY IT NEEDS A POLICY

Why open_uart needs a policy

Opening a UART connection creates a new persistent communication channel on hardware, which is a reversible write/setup action (it can be closed with close_uart). It does not yet send data or execute commands, but establishing the connection could enable subsequent operations on target hardware.

From the tool's definition 'Open a persistent UART connection and start an engagement'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

open_uart Rate-limited

open_uart stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "open_uart": {
      "limits": [
        {
          "counter": "open_uart_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about open_uart

What does the open_uart tool do? +

Open a persistent UART connection and start an engagement. It is categorised as a Write tool in the Buspirate MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on open_uart? +

Register the Buspirate MCP server in PolicyLayer and add a rule for open_uart: 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 Buspirate. Nothing to install.

What risk level is open_uart? +

open_uart is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit open_uart? +

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

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

open_uart is provided by the Buspirate MCP server (mplogas/buspirate-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.