sfiles_add_unit

THE RISK

Medium Risk

Why sfiles_add_unit needs a policy

This tool creates new elements (unit operations) within process engineering flowsheets, which constitutes data creation/modification without irreversible deletion or external financial/execution effects. It is a Write operation rather than Execute because it operates on structured diagram data, not arbitrary code or commands.

From the tool's definition Tool name 'sfiles_add_unit' and description 'Add a unit operation to the flowsheet' indicate creation and modification of engineering diagram data structures. The action is reversible (units can be removed or modified).

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

POLICY

How to control sfiles_add_unit

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_unit:

policy.json

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

sfiles_add_unit 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.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Engineering MCP Server tools

Destructive layout_delete Delete a layout from the store Execute layout_compute Compute layout for a model using ELK. Produces orthogonal edge routing suitable for P&ID d Execute model_batch_apply Execute multiple operations in a single call for efficiency Execute rules_apply Apply validation rules and return structured issues for LLM processing. Optionally auto-fi Write area_deploy Deploy a template into a model (STRATEGIC operation - replaces 50+ atomic calls) Write model_tx_begin Start a transaction on a model for atomic multi-operation changes Write model_combine Merge multiple DEXPI models into one combined model. Combines all tagged plant items, inst Write model_load Import a model from various formats (JSON, Proteus XML, SFILES string) - Replaces dexpi_im

All 72 Engineering MCP Server tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

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_unit

What does the sfiles_add_unit tool do? +

[Available via model_tx_apply or direct call] Add a unit operation to the 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_unit? +

Register the Engineering MCP Server MCP server in PolicyLayer and add a rule for sfiles_add_unit: 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_unit? +

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

Can I rate-limit sfiles_add_unit? +

Yes. Add a rate_limit block to the sfiles_add_unit 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_unit completely? +

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

sfiles_add_unit 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.

CHECK YOUR STACK →