AI agents call get_epub_path to retrieve information from Calibre without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves file path metadata for an existing EPUB file. It is a read-only query operation that returns information about data without creating, modifying, deleting, or executing anything. The blast radius of misuse is minimal—an attacker gains only the file path, not the file itself or any system access. Severity is low because knowing a file path alone does not compromise the Calibre library or the system.
From the tool's definition Tool name 'get_epub_path' and description 'Get the absolute file path of a book's EPUB file' indicate a retrieval operation with no modification or side effects.
Attacks that exploit this kind of access
Get the absolute file path of a book's EPUB file. It is categorised as a Read tool in the Calibre MCP Server, which means it retrieves data without modifying state.
Register the Calibre MCP server in PolicyLayer and add a rule for get_epub_path: 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 Calibre. Nothing to install.
get_epub_path is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the get_epub_path 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 get_epub_path. 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.
get_epub_path is provided by the Calibre MCP server (xmkevinchen/calibre-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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