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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is clear. The description adds useful detail about output units, but does not disclose calendar conventions such as inclusive/exclusive day counting or how partial months/years are handled, which are relevant behavioral traits beyond the 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 front-loaded sentence with no wasted text. It conveys the core operation and all output units efficiently.

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?

For a low-complexity, two-parameter date calculation tool with full schema coverage, annotations, and an output schema, the description is largely complete. The main remaining contextual gap is sibling differentiation, but most return-value and parameter details are handled by structured fields.

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 description coverage is 100%, and both parameters are clearly defined with examples and a preferred format, so the schema carries the parameter burden. The description mentions the output units but adds no extra semantics for start_date or end_date beyond what the schema already provides; baseline 3 is appropriate.

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 the operation (date difference) and the units returned (days, weeks, calendar years/months/days), so an agent can understand what the tool does. It does not, however, distinguish this from nearby siblings such as calculator_time_difference, calculator_days, or calculator_age, which all involve date/time intervals.

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?

There is no explicit guidance on when to use this tool versus alternatives. Given the many date/time-adjacent siblings, an agent would benefit from knowing whether this tool is intended for calendar-date differences while time_difference handles clock times, or how it differs from days/age.

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