AI agents use set_theme_mode to create or update resources in MCP Windows — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP Windows environment.
This tool creates or modifies system theme preference settings reversibly. It is a Write operation because it changes user-facing system configuration that can be easily reverted. Severity is low because theme changes have no impact on data integrity, financial systems, or critical operations—they are cosmetic UI preferences.
From the tool's definition Tool named 'set_theme_mode' with empty description, but context indicates it modifies Windows theme settings (as listed under 'theme settings' in server capabilities). The 'set_' prefix indicates a modification operation.
Documented attack patterns abuse exactly the kind of access set_theme_mode gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP Windows, and nothing reaches the server without passing your rules. This is the rule we recommend for set_theme_mode:
{
"version": "1",
"default": "deny",
"tools": {
"set_theme_mode": {
"limits": [
{
"counter": "set_theme_mode_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_theme_mode 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.
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set_theme_mode. It is categorised as a Write tool in the MCP Windows MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the MCP Windows MCP server in PolicyLayer and add a rule for set_theme_mode: 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 MCP Windows. Nothing to install.
set_theme_mode is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the set_theme_mode 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.
Set action: deny in the PolicyLayer policy for set_theme_mode. 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.
set_theme_mode is provided by the MCP Windows MCP server (secretiveshell/mcp-windows). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MCP Windows, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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28 MCP Windows tools catalogued and risk-classified — across an index of 43,000+ MCP servers.