Exact day-count fraction between two dates under a market convention. Dates are ISO YYYY-MM-DD. For ACT/ACT ICMA also pass frequency (coupons per year) and, for stub periods, the reference period boundaries. Deterministic; do not estimate this with a model.
AI agents call day_count_fraction 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 is a pure computational read operation. It takes date inputs and conventions as parameters and deterministically returns a calculated day-count fraction—a numeric query result with no side effects. There is no data creation, modification, deletion, code execution, or financial transaction.
From the tool's definition Tool computes and returns 'exact day-count fraction between two dates under a market convention' with no modification, deletion, creation, or execution of external operations.
Attacks that exploit this kind of access
Exact day-count fraction between two dates under a market convention. Dates are ISO YYYY-MM-DD. For ACT/ACT ICMA also pass frequency (coupons per year) and, for stub periods, the reference period boundaries. Deterministic; do not estimate this with a model. 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 day_count_fraction: 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.
day_count_fraction 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 day_count_fraction 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 day_count_fraction. 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.
day_count_fraction 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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