get-tag-values

THE RISK

Low Risk

Why get-tag-values needs a policy

This tool retrieves real-time or historical SCADA tag data without modifying it. However, severity is elevated to 'medium' rather than 'low' because unauthorized access to SCADA tag values in industrial control systems can expose sensitive operational data (equipment states, pressures, temperatures, system status) that could inform attacks on physical infrastructure.

From the tool's definition Tool description states it 'Retrieves tag values' from SCADA systems. The name 'get-tag-values' and verb 'Retrieves' indicate a read-only operation with no data modification.

Documented attack patterns abuse exactly the kind of access get-tag-values gives an agent:

POLICY

How to control get-tag-values

PolicyLayer is an MCP gateway — it sits between your AI agents and WinCC Unified MCP XT, and nothing reaches the server without passing your rules. This is the rule we recommend for get-tag-values:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "get-tag-values": {}
  }
}

get-tag-values 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 WinCC Unified MCP XT — 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

More WinCC Unified MCP XT tools

Execute reset-alarms Resets one or more active alarms based on their identifiers. Execute acknowledge-alarms Acknowledges one or more active alarms based on their identifiers. Write write-tag-values Updates tag values based on a provided list of TagValueInput entries. Read browse-objects Retrieves tags, elements, types, alarms, logging tags, and other named objects based on sp Read get-active-alarms Retrieves active alarms from the specified systems. Read get-logged-alarms Retrieves historical (logged) alarms from the storage system. Read get-logged-tag-values Retrieves historical tag values from the database for the specified tags or logging tags. Other login-user Authenticates a user in WinCC Unified using a provided username and password.

All 9 WinCC Unified MCP XT tools →

Read tools on other servers

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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 get-tag-values

What does the get-tag-values tool do? +

Retrieves tag values from WinCC Unified based on the provided names or filter criteria. It is categorised as a Read tool in the WinCC Unified MCP XT MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on get-tag-values? +

Register the WinCC Unified MCP XT MCP server in PolicyLayer and add a rule for get-tag-values: 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 WinCC Unified MCP XT. Nothing to install.

What risk level is get-tag-values? +

get-tag-values is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit get-tag-values? +

Yes. Add a rate_limit block to the get-tag-values 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 get-tag-values completely? +

Set action: deny in the PolicyLayer policy for get-tag-values. 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 get-tag-values? +

get-tag-values is provided by the WinCC Unified MCP XT MCP server (mrwan84/wincc-unified-mcp-xt). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every WinCC Unified MCP XT tool call.

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

CHECK YOUR STACK →