unblock_host · Defined MCP: Risk & Policy

WHAT IT DOES

What unblock_host does on Defined

AI agents use unblock_host 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 unblock_host needs a policy

The tool modifies network access control by unblocking a previously blocked host. While reversal of a destructive action (unblock is opposite of block), the operation itself is not destructive—it restores access and is reversible by re-blocking.

From the tool's definition Unblock a host, allowing it to rejoin the network. This reverses a prior blocking action and modifies the network access state of a host, making it a write operation that changes system configuration.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

unblock_host Rate-limited

unblock_host 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": {
    "unblock_host": {
      "limits": [
        {
          "counter": "unblock_host_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 unblock_host

What does the unblock_host tool do? +

Unblock a host, allowing it to rejoin the network. 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 unblock_host? +

Register the Defined MCP server in PolicyLayer and add a rule for unblock_host: 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 unblock_host? +

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

Can I rate-limit unblock_host? +

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

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

unblock_host 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.