apply_firewall_to_resources · Hcloud MCP: Risk & Policy

WHAT IT DOES

What apply_firewall_to_resources does on Hcloud

AI agents use apply_firewall_to_resources 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 apply_firewall_to_resources needs a policy

The tool creates or modifies firewall associations on cloud servers, which is a Write operation (reversible configuration change). While it affects security posture and has significant blast radius if misapplied to wrong resources, it is not Destructive (not irreversible), Execute (not running arbitrary code), or Financial.

From the tool's definition apply_firewall_to_resources applies a firewall to servers or resources via label selector. This modifies network security policies on cloud infrastructure—a reversible change that affects resource configurations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

apply_firewall_to_resources Rate-limited

apply_firewall_to_resources 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": {
    "apply_firewall_to_resources": {
      "limits": [
        {
          "counter": "apply_firewall_to_resources_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 apply_firewall_to_resources

What does the apply_firewall_to_resources tool do? +

Apply a firewall to servers or a label selector. Pass apply_to: [{ type:. 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 apply_firewall_to_resources? +

Register the Hcloud MCP server in PolicyLayer and add a rule for apply_firewall_to_resources: 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 apply_firewall_to_resources? +

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

Can I rate-limit apply_firewall_to_resources? +

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

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

apply_firewall_to_resources 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.