Use this method to acknowledge individual alarms. To call the Alarms.Acknowledge method, you need the
AI agents use Alarms-Acknowledge to create or update resources in ThinkPLC-MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your ThinkPLC-MCP environment.
Acknowledging alarms is a write operation that changes the acknowledgment state of alarms in the PLC. While it has real-world implications in industrial control systems (suppressing active alarm indicators), it is a reversible state change rather than destructive. However, in an industrial/SCADA context, incorrectly acknowledging alarms could mask real equipment faults, giving it medium severity.
From the tool's definition 'acknowledge individual alarms' — acknowledging an alarm is a state change (marking it as seen/acknowledged) on the PLC alarm system, which is reversible in the sense that alarms can be re-raised, but modifies the alarm acknowledgment state.
Documented attack patterns abuse exactly the kind of access Alarms-Acknowledge gives an agent:
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 Alarms-Acknowledge:
{
"version": "1",
"default": "deny",
"tools": {
"Alarms-Acknowledge": {
"limits": [
{
"counter": "alarms-acknowledge_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}Alarms-Acknowledge 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.
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Use this method to acknowledge individual alarms. To call the Alarms.Acknowledge method, you need the. It is categorised as a Write tool in the ThinkPLC-MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the ThinkPLC- MCP server in PolicyLayer and add a rule for Alarms-Acknowledge: 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.
Alarms-Acknowledge is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the Alarms-Acknowledge 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.
Set action: deny in the PolicyLayer policy for Alarms-Acknowledge. 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.
Alarms-Acknowledge 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.
Start from ThinkPLC-MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
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