emit_custom_event

THE RISK

High Risk

Why emit_custom_event needs a policy

Emitting a custom event triggers an external operation whose effects depend on the arguments passed. In a CAD environment integrated with AI assistants, custom events can trigger arbitrary actions or workflows within FreeCAD. The description is minimal, lowering confidence, but 'emit' implies firing a side-effecting signal rather than reading data.

From the tool's definition 'Emit a custom event' - triggers an external operation/event within FreeCAD

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

POLICY

How to control emit_custom_event

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 emit_custom_event:

policy.json

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

emit_custom_event 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 Mcp Freecad — 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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All 34 Mcp Freecad tools →

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Go deeper

High-risk tools in Mcp Freecad → Every high-risk tool this server exposes, in one view.
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.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about emit_custom_event

What does the emit_custom_event tool do? +

Emit a custom event. It is categorised as a Execute tool in the Mcp Freecad MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on emit_custom_event? +

Register the Mcp Freecad MCP server in PolicyLayer and add a rule for emit_custom_event: 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.

What risk level is emit_custom_event? +

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

Can I rate-limit emit_custom_event? +

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

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

emit_custom_event 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.

Enforce policy on every Mcp Freecad tool call.

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

CHECK YOUR STACK →