Add a book to a shelf in Calibre-Web
AI agents use crow_calibreweb_add_to_shelf to create or update resources in Crow — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Crow environment.
This tool creates or modifies data in a library management system by adding a book to a shelf. It is clearly a Write operation—it changes state but is fully reversible (the book can be removed from the shelf later). The blast radius is low because it affects only a local book shelf in Calibre-Web with no financial, destructive, or execution side effects.
From the tool's definition Tool name includes 'add_to' and description states 'Add a book to a shelf', which is a reversible modification operation (books can be removed from shelves).
Documented attack patterns abuse exactly the kind of access crow_calibreweb_add_to_shelf gives an agent:
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_calibreweb_add_to_shelf:
{
"version": "1",
"default": "deny",
"tools": {
"crow_calibreweb_add_to_shelf": {
"limits": [
{
"counter": "crow_calibreweb_add_to_shelf_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}crow_calibreweb_add_to_shelf stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Add a book to a shelf in Calibre-Web. It is categorised as a Write tool in the Crow MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Crow MCP server in PolicyLayer and add a rule for crow_calibreweb_add_to_shelf: 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.
crow_calibreweb_add_to_shelf is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the crow_calibreweb_add_to_shelf 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.
Set action: deny in the PolicyLayer policy for crow_calibreweb_add_to_shelf. 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.
crow_calibreweb_add_to_shelf 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.
Start from Crow, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
576 Crow tools catalogued and risk-classified — across an index of 43,000+ MCP servers.