select_by_valence · Blender MCP: Risk & Policy

WHAT IT DOES

What select_by_valence does on BlenderMCP

AI agents invoke select_by_valence to trigger actions in BlenderMCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why select_by_valence needs a policy

This tool performs an operation within Blender's 3D environment — selecting vertices based on a valence threshold. While 'select' sounds like a Read operation, it actively modifies the selection state within Blender, triggering side effects in the application's state. It doesn't retrieve/return data passively; it executes an action inside the Blender environment.

From the tool's definition Select vertices with valence (edge count) >= threshold

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

select_by_valence Rate-limited

select_by_valence 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.

View as policy code

policy.json

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

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about select_by_valence

What does the select_by_valence tool do? +

Select vertices with valence (edge count) >= threshold. It is categorised as a Execute tool in the BlenderMCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on select_by_valence? +

Register the Blender MCP server in PolicyLayer and add a rule for select_by_valence: 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 BlenderMCP. Nothing to install.

What risk level is select_by_valence? +

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

Can I rate-limit select_by_valence? +

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

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

select_by_valence is provided by the Blender MCP server (shirshovdim/retopoflow_blender_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.