set_background · ChimeraX MCP Server MCP: Risk & Policy

WHAT IT DOES

What set_background does on ChimeraX MCP Server

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

WHY IT NEEDS A POLICY

Why set_background needs a policy

This tool modifies the display properties of the ChimeraX environment by changing the background color. It creates or modifies display settings reversibly—the user can change the background color back to a previous state at any time. This is a non-destructive modification of the visualization state, not data deletion, code execution, or financial action.

From the tool's definition Tool name 'set_background' and description 'Set the background color (white, black, hex)' indicate modification of visualization state (background color) within ChimeraX.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_background Rate-limited

set_background 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": {
      "limits": [
        {
          "counter": "set_background_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 ChimeraX MCP Server, so you can run agents against it safely.

FAQ

Questions about set_background

What does the set_background tool do? +

Set the background color (white, black, hex). It is categorised as a Write tool in the ChimeraX MCP Server 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? +

Register the ChimeraX MCP Server MCP server in PolicyLayer and add a rule for set_background: 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 ChimeraX MCP Server. Nothing to install.

What risk level is set_background? +

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

Can I rate-limit set_background? +

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

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

set_background is provided by the ChimeraX MCP Server MCP server (mahynotch/chimerax-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.