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

Annotations already declare readOnlyHint, non-destructive, and closed-world, so the safety profile is covered. The description does add one genuinely useful behavioral fact — that years are treated as Julian years of 365.25 days — but says nothing about rounding/precision or output format.

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?

A single front-loaded sentence with the verb first, the unit list second, and the one non-obvious convention (Julian year) parenthetically attached. No filler.

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?

With annotations and an output schema present, the description need only cover unit scope and conventions, and it does both. Minor gap: it doesn't say whether months or milliseconds are unsupported, so an agent could attempt an invalid unit and only learn from the error.

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 100%, but the property descriptions are near-placeholders ("Value.", "Source time unit.") and there are zero enums. The description supplies the actual accepted unit vocabulary (seconds, minutes, hours, days, weeks, years), which is the most important missing semantic and is exactly what the schema lacks.

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?

States a specific verb+resource ("Convert time") and enumerates the supported units, so an agent can immediately tell this is a unit-conversion tool rather than an arithmetic one. It does not explicitly distinguish itself from nearby siblings such as calculator_time_difference or calculator_days, which keeps it below a 5.

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 gives no when-to-use or when-not-to-use guidance and never mentions alternatives. An agent must infer from the tool name alone that this is for converting a quantity between time units rather than computing a difference or a date.

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