crow_calibre_browse_category

THE RISK

Low Risk

Why crow_calibre_browse_category needs a policy

This tool retrieves and queries book metadata from a library (Calibre). It has no side effects, does not modify data, does not execute code, and does not delete or overwrite anything. The blast radius of misuse is minimal — an AI agent could at worst retrieve unwanted book information, which poses no security or operational risk.

From the tool's definition Tool description states 'Browse books within a specific category' — this is a retrieval operation with no modification, deletion, or execution capability. The verb 'browse' and the context of querying books by author/tag/series indicate a read-only query.

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

POLICY

How to control crow_calibre_browse_category

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_calibre_browse_category:

policy.json

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

crow_calibre_browse_category 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_calibre_browse_category

What does the crow_calibre_browse_category tool do? +

Browse books within a specific category (e.g., a particular author, tag, or series). 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_calibre_browse_category? +

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

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

Can I rate-limit crow_calibre_browse_category? +

Yes. Add a rate_limit block to the crow_calibre_browse_category 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_calibre_browse_category completely? +

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

crow_calibre_browse_category 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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