set_material · Blender MCP: Risk & Policy

WHAT IT DOES

What set_material does on BlenderMCP

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

WHY IT NEEDS A POLICY

Why set_material needs a policy

This tool modifies object properties (materials) in a 3D scene. Materials can be changed or removed, making this a reversible Write operation rather than destructive. The blast radius is medium because an AI agent could apply unwanted materials to many objects, but the changes are undoable and do not delete or permanently destroy data.

From the tool's definition Tool name 'set_material' and description 'Set or create a material for an object' indicate creation or modification of object properties in Blender, which are reversible changes.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_material Rate-limited

set_material 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": {
    "set_material": {
      "limits": [
        {
          "counter": "set_material_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 BlenderMCP, so you can run agents against it safely.

FAQ

Questions about set_material

What does the set_material tool do? +

Set or create a material for an object. It is categorised as a Write tool in the BlenderMCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_material? +

Register the Blender MCP server in PolicyLayer and add a rule for set_material: 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 set_material? +

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

Can I rate-limit set_material? +

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

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

set_material is provided by the Blender MCP server (richard-devbot/blender-mcp-csm). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.