add_domain · Mcp Pihole MCP: Risk & Policy

WHAT IT DOES

What add_domain does on Mcp Pihole

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

WHY IT NEEDS A POLICY

Why add_domain needs a policy

This tool creates or modifies DNS filtering rules by adding domains to allow/deny lists. While reversible (domains can be removed), it directly impacts network traffic filtering for all devices on the Pi-hole network. Misuse could allow malicious domains through (adding to allowlist) or block legitimate services (adding to denylist), affecting multiple users.

From the tool's definition Tool description explicitly states 'Add a domain to the allow or deny list.' This is a modification operation that creates or updates DNS blocking rules. The server description confirms it manages 'domain allow/deny lists.'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_domain Rate-limited

add_domain 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": {
    "add_domain": {
      "limits": [
        {
          "counter": "add_domain_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 Mcp Pihole, so you can run agents against it safely.

FAQ

Questions about add_domain

What does the add_domain tool do? +

Add a domain to the allow or deny list. It is categorised as a Write tool in the Mcp Pihole MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_domain? +

Register the Mcp Pihole MCP server in PolicyLayer and add a rule for add_domain: 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 Pihole. Nothing to install.

What risk level is add_domain? +

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

Can I rate-limit add_domain? +

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

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

add_domain is provided by the Mcp Pihole MCP server (obrien-matthew/mcp-pihole). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.