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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds useful context by enumerating the unit breakdowns returned, but it does not say whether the result is signed or absolute, which date is subtracted from which, or how partial months/years are resolved.

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 tight sentence with no filler, and the most decision-relevant information (the units returned) is front-loaded. It is terse rather than padded, though the fragment form costs a little clarity.

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 two-parameter, non-destructive calculation with no output schema, the description covers the essentials but leaves open the direction of the subtraction and the handling of negative intervals — details an agent would want before calling it.

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% and both parameters are documented as YYYY-MM-DD, so the schema carries the load. The description adds nothing about the two parameters, and the baseline of 3 applies.

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 names the resource (two dates) and the computed quantity (days, weeks, calendar years/months/days between them), which is enough to separate it from siblings like calculate_age and timestamp_convert. It lacks an explicit verb, so the phrasing reads as a noun fragment, but the operation is unambiguous.

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 guidance on when to pick this over calculate_age (age from a birthdate) or timestamp_convert, which are the closest siblings. The agent must infer the choice from the tool name alone.

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