Plc-ReadSystemTime

THE RISK

Low Risk

Why Plc-ReadSystemTime needs a policy

This tool queries and returns the current system time from a PLC controller. It is a read-only operation that retrieves data without altering state, executing commands, or causing destructive effects. The low severity reflects minimal blast radius—an AI agent misusing this tool could only obtain time information, which poses no operational, data integrity, or safety risk.

From the tool's definition Tool name 'Plc-ReadSystemTime' and description explicitly state it 'provides the system time of the CPU' — a retrieval operation with no modification or side effects.

Documented attack patterns abuse exactly the kind of access Plc-ReadSystemTime gives an agent:

POLICY

How to control Plc-ReadSystemTime

PolicyLayer is an MCP gateway — it sits between your AI agents and ThinkPLC-MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for Plc-ReadSystemTime:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "Plc-ReadSystemTime": {}
  }
}

Plc-ReadSystemTime is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register ThinkPLC-MCP — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

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EXPLORE

Related tools and policies

More ThinkPLC-MCP tools

Execute Api-Logout The Api.Logout method removes the token from the list of active Web API sessions and ends Execute Plc-RequestChangeOperatingMode With the Plc.RequestChangeOperatingMode method, you request a new operating mode forthe CP Write Alarms-Acknowledge Use this method to acknowledge individual alarms. To call the Alarms.Acknowledge method, y Write Api-ChangePassword You can change the password for a user account with the Api.ChangePassword method. Recomme Write Api-Login The Api.Login method checks the login data of the user and on successful verification open Write Plc-SetSystemTime Use this API method to set the system time of the CPU (PLC local time). To call the Plc.Se Write PlcProgram-Write-Boolean Use the PlcProgram.Write method to write a single process tag to the CPU. To call the PlcP Write PlcProgram-Write-Number Use the PlcProgram.Write method to write a single process tag to the CPU. To call the PlcP

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about Plc-ReadSystemTime

What does the Plc-ReadSystemTime tool do? +

This API method provides the system time of the CPU. If you have synchronized the system time of the CPU, for example via the TIA Portal function. It is categorised as a Read tool in the ThinkPLC-MCP MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on Plc-ReadSystemTime? +

Register the ThinkPLC- MCP server in PolicyLayer and add a rule for Plc-ReadSystemTime: 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 ThinkPLC-MCP. Nothing to install.

What risk level is Plc-ReadSystemTime? +

Plc-ReadSystemTime is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit Plc-ReadSystemTime? +

Yes. Add a rate_limit block to the Plc-ReadSystemTime 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 Plc-ReadSystemTime completely? +

Set action: deny in the PolicyLayer policy for Plc-ReadSystemTime. 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 Plc-ReadSystemTime? +

Plc-ReadSystemTime is provided by the ThinkPLC- MCP server (mrwan84/thinkplc-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every ThinkPLC-MCP tool call.

Start from ThinkPLC-MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →