set_dns · Mullvad MCP: Risk & Policy

WHAT IT DOES

What set_dns does on Mullvad

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

WHY IT NEEDS A POLICY

Why set_dns needs a policy

DNS configuration changes are reversible writes that affect network behavior. While not destructive, misconfigured DNS (e.g., pointing to malicious resolvers) could enable man-in-the-middle attacks or data exfiltration, warranting medium severity. Confidence is moderate (0.75) due to the empty tool description, which limits certainty about exact behavior and constraints.

From the tool's definition Tool name 'set_dns' indicates modification of DNS settings. The tool description is empty, but based on the server's purpose (controlling Mullvad VPN) and sibling tools like 'get_settings', this clearly modifies VPN configuration rather than reading or…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_dns Rate-limited

set_dns 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_dns": {
      "limits": [
        {
          "counter": "set_dns_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 Mullvad, so you can run agents against it safely.

FAQ

Questions about set_dns

What does the set_dns tool do? +

set_dns. It is categorised as a Write tool in the Mullvad 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_dns? +

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

What risk level is set_dns? +

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

Can I rate-limit set_dns? +

Yes. Add a rate_limit block to the set_dns 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_dns completely? +

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

set_dns is provided by the Mullvad MCP server (oresam-xyz/mullvad-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.