AI agents call get_calendar_filters to retrieve information from N Lobby MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool retrieves filter metadata for calendar views. This is a read-only operation that returns configuration or filter options without modifying data, executing code, or affecting system state. The low severity reflects minimal blast radius if misused—an AI agent could only retrieve available filters, not access unauthorized data or trigger actions.
From the tool's definition Tool name 'get_calendar_filters' and description 'Get lobby calendar filter list' indicate a retrieval operation with no mutation or side effects. This queries filtering options for calendar data.
Documented attack patterns abuse exactly the kind of access get_calendar_filters gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and N Lobby MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for get_calendar_filters:
{
"version": "1",
"default": "deny",
"tools": {
"get_calendar_filters": {}
}
}get_calendar_filters is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get lobby calendar filter list. It is categorised as a Read tool in the N Lobby MCP Server MCP Server, which means it retrieves data without modifying state.
Register the N Lobby MCP Server MCP server in PolicyLayer and add a rule for get_calendar_filters: 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 N Lobby MCP Server. Nothing to install.
get_calendar_filters 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_calendar_filters 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_calendar_filters. 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_calendar_filters is provided by the N Lobby MCP Server MCP server (minagishl/nlobby-cli). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from N Lobby MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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28 N Lobby MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.