sfiles_add_control

THE RISK

Medium Risk

Why sfiles_add_control needs a policy

This tool creates or adds new control instrumentation elements to process engineering diagrams. While it modifies diagram data, it is reversible (elements can be removed or edited) and does not delete data or trigger external operations. This places it in the Write category.

From the tool's definition Tool name 'sfiles_add_control' and description 'Add control instrumentation to flowsheet' indicate creating or modifying diagram elements.

Documented attack patterns abuse exactly the kind of access sfiles_add_control gives an agent:

POLICY

How to control sfiles_add_control

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "sfiles_add_control": {
      "limits": [
        {
          "counter": "sfiles_add_control_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

sfiles_add_control 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.

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

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EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about sfiles_add_control

What does the sfiles_add_control tool do? +

[Available via model_tx_apply or direct call] Add control instrumentation to flowsheet. See docs/FEATURE_PARITY_MATRIX.md for migration guide. It is categorised as a Write tool in the Engineering MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on sfiles_add_control? +

Register the Engineering MCP Server MCP server in PolicyLayer and add a rule for sfiles_add_control: 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 Engineering MCP Server. Nothing to install.

What risk level is sfiles_add_control? +

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

Can I rate-limit sfiles_add_control? +

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

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

sfiles_add_control is provided by the Engineering MCP Server MCP server (puran-water/dexpi-sfiles-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Engineering MCP Server tool call.

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

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