add_firewall_rule · Defined MCP: Risk & Policy

WHAT IT DOES

What add_firewall_rule does on Defined

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

WHY IT NEEDS A POLICY

Why add_firewall_rule needs a policy

Adding a firewall rule creates a new security policy that modifies network behavior. This is reversible (rules can be removed or modified) and has no financial impact, placing it in Write rather than Execute or Destructive. The severity is high because misconfigured firewall rules could block legitimate traffic or expose systems.

From the tool's definition Tool name 'add_firewall_rule' indicates creation of firewall rules. Sibling tools include 'add_route_firewall_rule' and 'add_host_tag', which are clearly Write operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_firewall_rule Rate-limited

add_firewall_rule 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_firewall_rule": {
      "limits": [
        {
          "counter": "add_firewall_rule_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 Defined, so you can run agents against it safely.

FAQ

Questions about add_firewall_rule

What does the add_firewall_rule tool do? +

add_firewall_rule. It is categorised as a Write tool in the Defined 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_firewall_rule? +

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

What risk level is add_firewall_rule? +

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

Can I rate-limit add_firewall_rule? +

Yes. Add a rate_limit block to the add_firewall_rule 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_firewall_rule completely? +

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

add_firewall_rule is provided by the Defined MCP server (quickvm/defined-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.