set_theme · HoloViz MCP Server MCP: Risk & Policy

WHAT IT DOES

What set_theme does on HoloViz MCP Server

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

WHY IT NEEDS A POLICY

Why set_theme needs a policy

This tool modifies the visual presentation state of an existing chart by changing its theme. While it creates a side effect (the chart's appearance changes), this modification is reversible and non-destructive. It does not read sensitive data, execute arbitrary code, delete anything, or create financial obligations.

From the tool's definition Tool name 'set_theme' and description 'Switch a chart between dark and light theme' indicate modification of visualization appearance settings.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_theme Rate-limited

set_theme 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_theme": {
      "limits": [
        {
          "counter": "set_theme_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 HoloViz MCP Server, so you can run agents against it safely.

FAQ

Questions about set_theme

What does the set_theme tool do? +

Switch a chart between dark and light theme. It is categorised as a Write tool in the HoloViz 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_theme? +

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

What risk level is set_theme? +

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

Can I rate-limit set_theme? +

Yes. Add a rate_limit block to the set_theme 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_theme completely? +

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

set_theme is provided by the HoloViz MCP Server MCP server (sumayabee/holoviz-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.