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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and determinism are covered. The description adds the useful detail that results are expressed in years/months/days, but says nothing about default end date, accepted date formats, or timezone handling.

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 em-dash-joined line with the output units front-loaded after the resource name. No waste, though the compression is partly what leaves the parameter gaps.

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 tool with no output schema and zero schema descriptions, the description should at minimum pin down the optional endDate default and the date string format. Neither appears, so an agent could easily call it with an unsupported format or a missing-but-expected end date.

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 0% for both parameters, so the description must carry the semantics and does not: it never says endDate is optional, what happens if it is omitted, what string format dates take, or whether order matters. 'Between dates' only hints that two inputs are involved.

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?

'Age calculator' plus 'years/months/days between dates' specifies both the operation and the unit granularity of the result, so an agent knows this computes a duration rather than a single number. It stops short of distinguishing itself from date-range siblings such as converters_job_experience or converters_countdown.

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 statement of when to pick this over the many other calendar/date calculators in the sibling list, and no guidance on when endDate should be supplied versus omitted (presumably today). Usage must be inferred entirely from the one-line description.

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