crow_bookstack_shelves

THE RISK

Low Risk

Why crow_bookstack_shelves needs a policy

This tool performs a retrieval operation querying the BookStack shelves collection and returning counts. It does not create, modify, delete, execute code, or commit financial transactions. The blast radius is minimal—an AI agent misusing this tool could only potentially learn shelf organization or count information from BookStack, which is informational only.

From the tool's definition Tool name contains 'list' operation pattern (crow_bookstack_shelves) and description explicitly states 'List all shelves' — a read-only query that retrieves shelf metadata and book counts with no modification or side effects.

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

POLICY

How to control crow_bookstack_shelves

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_bookstack_shelves:

policy.json

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

crow_bookstack_shelves 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_bookstack_shelves

What does the crow_bookstack_shelves tool do? +

List all shelves in BookStack with book counts. 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_bookstack_shelves? +

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

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

Can I rate-limit crow_bookstack_shelves? +

Yes. Add a rate_limit block to the crow_bookstack_shelves 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_bookstack_shelves completely? +

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

crow_bookstack_shelves 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.

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