AI agents use export_step to create or update resources in Mcp Freecad — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Mcp Freecad environment.
This tool writes data to a file system artifact (STEP file export). While file creation is reversible and doesn't permanently destroy data, it modifies the file system state. It's less severe than Destructive (which would involve deleting or overwriting without recovery), and not Execute (which would run arbitrary code).
From the tool's definition Tool performs 'Export objects to STEP file' — creates and writes a file in STEP format, which is a reversible operation (the file can be modified or deleted).
Documented attack patterns abuse exactly the kind of access export_step gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Freecad, and nothing reaches the server without passing your rules. This is the rule we recommend for export_step:
{
"version": "1",
"default": "deny",
"tools": {
"export_step": {
"limits": [
{
"counter": "export_step_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}export_step 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.
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Export objects to STEP file. It is categorised as a Write tool in the Mcp Freecad MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Mcp Freecad MCP server in PolicyLayer and add a rule for export_step: 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 Mcp Freecad. Nothing to install.
export_step is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the export_step 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.
Set action: deny in the PolicyLayer policy for export_step. 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.
export_step is provided by the Mcp Freecad MCP server (jango-blockchained/mcp-freecad). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Mcp Freecad, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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34 Mcp Freecad tools catalogued and risk-classified — across an index of 43,000+ MCP servers.