subtractive_pipe

THE RISK

High Risk

In FreeCAD, 'Subtractive Pipe' is a PartDesign operation that sweeps a profile along a path to remove (subtract) material from a solid body. Based on context from the server (3D modeling) and FreeCAD's known toolset, this likely triggers a modeling operation.

From the tool's definition Tool name 'subtractive_pipe' in a FreeCAD 3D modeling MCP server with 150+ tools; description is empty.

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

HOW TO CONTROL SUBTRACTIVE_PIPE

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "subtractive_pipe": {
      "limits": [
        {
          "counter": "subtractive_pipe_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

subtractive_pipe stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register FreeCAD Robust 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.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

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All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

What does the subtractive_pipe tool do? +

subtractive_pipe. It is categorised as a Execute tool in the FreeCAD Robust MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on subtractive_pipe? +

Register the FreeCAD Robust MCP Server MCP server in PolicyLayer and add a rule for subtractive_pipe: 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 FreeCAD Robust MCP Server. Nothing to install.

What risk level is subtractive_pipe? +

subtractive_pipe is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit subtractive_pipe? +

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

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

subtractive_pipe is provided by the FreeCAD Robust MCP Server MCP server (spkane/freecad-addon-robust-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 FreeCAD Robust MCP Server tool call.

Deterministic rules across all 152 FreeCAD Robust MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.

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// WHAT SUBTRACTIVE_PIPE ON FREECAD ROBUST MCP SERVER DOES

// THE RISK

// HOW TO CONTROL SUBTRACTIVE_PIPE

// EXPLORE