preview_blacklist_add · AF_ MCP: Risk & Policy

WHAT IT DOES

What preview_blacklist_add does on AF_MCP

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

WHY IT NEEDS A POLICY

Why preview_blacklist_add needs a policy

The tool appears to preview adding entries to a blacklist, which modifies security device configuration reversibly. While the description is empty, the name and server context indicate it performs write operations on security policies. Classified as Write rather than Execute because it previews/stages changes rather than immediately executing them.

From the tool's definition Tool name 'preview_blacklist_add' and server context indicating 'device blocking and unblocking operations'. Sibling tool 'apply_blacklist_add' suggests this is a preview/staging operation for blacklist modifications.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

preview_blacklist_add Rate-limited

preview_blacklist_add 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": {
    "preview_blacklist_add": {
      "limits": [
        {
          "counter": "preview_blacklist_add_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 AF_MCP, so you can run agents against it safely.

FAQ

Questions about preview_blacklist_add

What does the preview_blacklist_add tool do? +

preview_blacklist_add. It is categorised as a Write tool in the AF_MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on preview_blacklist_add? +

Register the AF_ MCP server in PolicyLayer and add a rule for preview_blacklist_add: 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 AF_MCP. Nothing to install.

What risk level is preview_blacklist_add? +

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

Can I rate-limit preview_blacklist_add? +

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

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

preview_blacklist_add is provided by the AF_ MCP server (xiaqijun/af_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.