List all categories (directories) inside /Notes.
AI agents call list_categories to retrieve information from Nextcloud Notes without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and returns information about existing categories/directories without creating, modifying, deleting, or executing any operations. It is a pure read operation with minimal security impact, as it only exposes the structure of notes already stored in Nextcloud.
From the tool's definition Tool name is 'list_categories' and description states 'List all categories (directories) inside /Notes' — a retrieval operation with no side effects.
Attacks that exploit this kind of access
List all categories (directories) inside /Notes. It is categorised as a Read tool in the Nextcloud Notes MCP Server, which means it retrieves data without modifying state.
Register the Nextcloud Notes MCP server in PolicyLayer and add a rule for list_categories: 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 Nextcloud Notes. Nothing to install.
list_categories 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 list_categories 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 list_categories. 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.
list_categories is provided by the Nextcloud Notes MCP server (rncz/nextcloud-notes-mcp-server). 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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