AI agents call list_calendars to retrieve information from Shikamaru without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool simply enumerates supported holiday calendars and returns descriptive information. It performs a read-only query operation that neither modifies state, executes code, performs financial transactions, nor deletes data. The blast radius of misuse is minimal—an AI agent could only retrieve informational content about available calendars.
From the tool's definition Tool name 'list_calendars' and description 'List the supported holiday calendars with a one-line description of each' indicate retrieval/querying of calendar metadata with no side effects.
Attacks that exploit this kind of access
List the supported holiday calendars with a one-line description of each. It is categorised as a Read tool in the Shikamaru MCP Server, which means it retrieves data without modifying state.
Register the Shikamaru MCP server in PolicyLayer and add a rule for list_calendars: 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 Shikamaru. Nothing to install.
list_calendars 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_calendars 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_calendars. 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_calendars is provided by the Shikamaru MCP server (JayOfemi/shikamaru). 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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