set_background_color · Vmd MCP: Risk & Policy

WHAT IT DOES

What set_background_color does on Vmd

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

WHY IT NEEDS A POLICY

Why set_background_color needs a policy

This tool modifies a display/visual setting (background color) in the VMD application. It is a reversible configuration change with no data destruction, financial impact, or code execution. The blast radius of misuse is minimal — it only affects the visual appearance of the molecular viewer.

From the tool's definition Set the VMD background color, e.g. black, white, gray, blue.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_background_color Rate-limited

set_background_color 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_background_color": {
      "limits": [
        {
          "counter": "set_background_color_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 Vmd, so you can run agents against it safely.

FAQ

Questions about set_background_color

What does the set_background_color tool do? +

Set the VMD background color, e.g. black, white, gray, blue. It is categorised as a Write tool in the Vmd 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_background_color? +

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

What risk level is set_background_color? +

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

Can I rate-limit set_background_color? +

Yes. Add a rate_limit block to the set_background_color 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_background_color completely? +

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

set_background_color is provided by the Vmd MCP server (omararias-gaguancela/vmd-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.