Whether a date is a business day under a holiday calendar, with the reason when it is not (weekend or holiday). Calendars are rules in code (no stale data feed). Deterministic; do not let a model guess market holidays.
AI agents call is_business_day 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.
The tool is purely informational—it queries a calendar to determine if a date is a business day and returns the result. No data is created, modified, deleted, or externally executed. The function serves a read-only lookup purpose in a financial calculations engine. Low severity because misuse poses no operational or financial risk; an AI agent could repeatedly call it without causing harm.
From the tool's definition Tool description states it checks "Whether a date is a business day" and provides "the reason when it is not".
Attacks that exploit this kind of access
Whether a date is a business day under a holiday calendar, with the reason when it is not (weekend or holiday). Calendars are rules in code (no stale data feed). Deterministic; do not let a model guess market holidays. 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 is_business_day: 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.
is_business_day 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 is_business_day 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 is_business_day. 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.
is_business_day 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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