fw_unfollow

THE RISK

Critical Risk

Why fw_unfollow needs a policy

Removing a follow or subscription is an irreversible action (the subscription/follow relationship is deleted). While it can technically be re-followed, the act of removing/deleting the subscription record is destructive in nature. Medium severity because the blast radius is limited to social/subscription state rather than critical data.

From the tool's definition Remove a library follow or channel subscription

Documented attack patterns abuse exactly the kind of access fw_unfollow gives an agent:

POLICY

How to control fw_unfollow

PolicyLayer is an MCP gateway — it sits between your AI agents and Crow, and nothing reaches the server without passing your rules. This is the rule we recommend for fw_unfollow:

policy.json

{
  "version": "1",
  "default": "deny",
  "hide": [
    "fw_unfollow"
  ]
}

fw_unfollow disappears from the agent's tool list entirely, and any attempt to call it is denied. The rest of the server keeps working.

Create a free account and register Crow — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RESTRICT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

Critical-risk tools in Crow → Every critical-risk tool this server exposes, in one view.
All critical-risk MCP tools → Every critical-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Blast radius → How much damage one compromised or confused agent can do — and how to bound it.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about fw_unfollow

What does the fw_unfollow tool do? +

Remove a library follow or channel subscription. Rate-limited: 30/hour. It is categorised as a Destructive tool in the Crow MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.

How do I enforce a policy on fw_unfollow? +

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

What risk level is fw_unfollow? +

fw_unfollow is a Destructive tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.

Can I rate-limit fw_unfollow? +

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

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

fw_unfollow is provided by the Crow MCP server (kh0pper/crow). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Crow tool call.

Start from Crow, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →