crow_list_instances

THE RISK

Low Risk

Why crow_list_instances needs a policy

This tool queries and returns metadata about registered instances (name, hostname, directory, status, connectivity). It has no side effects, makes no modifications, and poses minimal risk even if misused by an agent—the worst outcome would be information disclosure of already-registered instance names and basic status information.

From the tool's definition Tool name 'crow_list_instances' and description 'List all registered Crow instances' clearly indicates a read-only operation that retrieves and displays instance information without modifying data.

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

POLICY

How to control crow_list_instances

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 crow_list_instances:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "crow_list_instances": {}
  }
}

crow_list_instances is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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.

CAP THIS TOOL →

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EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about crow_list_instances

What does the crow_list_instances tool do? +

List all registered Crow instances (local and remote). Shows instance name, hostname, directory, status, and whether it. It is categorised as a Read tool in the Crow MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on crow_list_instances? +

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

crow_list_instances is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit crow_list_instances? +

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

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

crow_list_instances 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 →