write_rtt · Jlink MCP: Risk & Policy

WHAT IT DOES

What write_rtt does on Jlink

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

WHY IT NEEDS A POLICY

Why write_rtt needs a policy

This tool writes/sends data to a microcontroller's RTT (Real-Time Transfer) input channel. It is a Write operation as it transmits data to the target device. Misuse could cause unintended behavior on the microcontroller (e.g., corrupting runtime state or triggering unintended commands), warranting medium severity.

From the tool's definition 向 RTT 输入通道发送数据（发送到目标单片机）— 'send data to RTT input channel (send to target microcontroller)'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

write_rtt Rate-limited

write_rtt 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": {
    "write_rtt": {
      "limits": [
        {
          "counter": "write_rtt_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 Jlink, so you can run agents against it safely.

FAQ

Questions about write_rtt

What does the write_rtt tool do? +

向 RTT 输入通道发送数据（发送到目标单片机）。. It is categorised as a Write tool in the Jlink MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on write_rtt? +

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

What risk level is write_rtt? +

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

Can I rate-limit write_rtt? +

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

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

write_rtt is provided by the Jlink MCP server (xun123456/jlink-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.