pf_block_domain

THE RISK

Critical Risk

Why pf_block_domain needs a policy

Blocking an entire remote domain cuts off all federation and media fetching from that domain, which is a significant and potentially irreversible network-level action affecting all users/services relying on that domain.

From the tool's definition Block an entire remote domain (no federation, no media fetch)

Risk signalsBulk/mass operation — affects multiple targets

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

POLICY

How to control pf_block_domain

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 pf_block_domain:

policy.json

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

pf_block_domain 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.
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FAQ

Questions about pf_block_domain

What does the pf_block_domain tool do? +

Block an entire remote domain (no federation, no media fetch). QUEUED — requires operator confirmation in the Nest panel. 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 pf_block_domain? +

Register the Crow MCP server in PolicyLayer and add a rule for pf_block_domain: 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 pf_block_domain? +

pf_block_domain 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 pf_block_domain? +

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

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

pf_block_domain 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 →