date_math

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description must convey behavioral traits. It does disclose the two modes and the business-day option, which adds context beyond the schema. However, it does not mention return format, timezone handling, or behavior when both add and end are supplied, leaving gaps for a tool with no annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, focused statement that starts with 'Date arithmetic' and immediately outlines the two modes. It uses clear formatting with inline code and examples without redundancy, earning its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool has no output schema, so the description should cover return values and edge cases. It explains the input combinations well but not the output format (e.g., date string vs. number of days) or error handling. Given the absence of annotations and output schema, this is a moderate gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 75% (three of four parameters have descriptions), so the description must compensate for the gap. It does by explaining the relationship between start, add, and end, and clarifying the role of business_days in diff mode. The examples supplement the schema's parameter descriptions, adding meaningful usage context.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Date arithmetic' and enumerates two distinct modes with concrete examples, making the tool's purpose unambiguous. It also differentiates from sibling tools by specifying its unique capabilities (adding durations and computing diffs, with business-day option). While it doesn't name alternatives, the scope is precise.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly describes when to use each mode: provide start+add to compute a resulting date, or start+end to compute the diff. It also notes that diff mode optionally counts business days only. However, it doesn't reference sibling tools like age_calc or explicitly state exclusions, so it falls short of a perfect 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.