update_firewall · Hcloud MCP: Risk & Policy

WHAT IT DOES

What update_firewall does on Hcloud

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

WHY IT NEEDS A POLICY

Why update_firewall needs a policy

This tool modifies firewall properties (name and labels) but does not delete or irreversibly destroy firewall rules or resources. The changes are reversible through subsequent updates. While firewalls are security-critical infrastructure, the blast radius is limited to metadata/labeling changes rather than rule modifications or infrastructure destruction.

From the tool's definition Tool name is 'update_firewall' and description states it can 'Update a firewall (name, labels)' — these are reversible modifications to firewall configuration attributes.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_firewall Rate-limited

update_firewall 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": {
    "update_firewall": {
      "limits": [
        {
          "counter": "update_firewall_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 Hcloud, so you can run agents against it safely.

FAQ

Questions about update_firewall

What does the update_firewall tool do? +

Update a firewall (name, labels). It is categorised as a Write tool in the Hcloud MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_firewall? +

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

What risk level is update_firewall? +

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

Can I rate-limit update_firewall? +

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

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

update_firewall is provided by the Hcloud MCP server (xodus-co/hcloud-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.