bim_create_wall · FreeCAD MCP: Risk & Policy

WHAT IT DOES

What bim_create_wall does on FreeCAD MCP

AI agents use bim_create_wall to create or update resources in FreeCAD MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your FreeCAD MCP environment.

WHY IT NEEDS A POLICY

Why bim_create_wall needs a policy

This tool creates (writes) a new wall object in a FreeCAD BIM model. It is reversible — walls can be deleted or modified after creation. It does not execute arbitrary code, delete data irreversibly, or commit financial transactions. The primary risk is misuse by an AI agent to create unwanted or structurally invalid walls in a design, requiring human review/correction.

From the tool's definition Tool name is 'bim_create_wall' — the verb 'create' indicates it adds new data to a CAD model. This is a Building Information Modeling (BIM) operation that mirrors sibling tools like bim_create_column, bim_create_door, bim_create_roof, bim_create_slab, and…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

bim_create_wall Rate-limited

bim_create_wall 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches FreeCAD MCP, so you can run agents against it safely.

FAQ

Questions about bim_create_wall

What does the bim_create_wall tool do? +

bim_create_wall. It is categorised as a Write tool in the FreeCAD MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on bim_create_wall? +

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

What risk level is bim_create_wall? +

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

Can I rate-limit bim_create_wall? +

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

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

bim_create_wall is provided by the FreeCAD MCP server (sandraschi/freecad-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.