AI agents call list_plcs to retrieve information from Wago Plc without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool is a read operation that queries and retrieves a list of PLC devices from the network. However, the severity is elevated to 'medium' rather than 'low' because the information disclosed (reachable PLCs in the network) could be valuable for reconnaissance by a malicious agent seeking to identify industrial control systems to target.
From the tool's definition The tool description states 'List all reachable WAGO PLCs' which retrieves information about available devices without modifying or executing operations. The name 'list_plcs' is consistent with read operations (list, get, fetch patterns).
Attacks that exploit this kind of access
List all reachable WAGO PLCs. Use first to find a target IP. It is categorised as a Read tool in the Wago Plc MCP Server, which means it retrieves data without modifying state.
Register the Wago Plc MCP server in PolicyLayer and add a rule for list_plcs: 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 Wago Plc. Nothing to install.
list_plcs is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_plcs 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 list_plcs. 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.
list_plcs is provided by the Wago Plc MCP server (wagoalex/wago-plc-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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