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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds real value beyond that: it declares the exact output set (change, rate per day/week/30 days) and explicitly scopes out reference comparison, preventing misuse as a percentile tool.

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?

Front-loads what is computed, then examples, then units, then the scope limitation. Three tight sentences with no filler and no repetition.

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 no output schema, the description must describe returns, and it does so explicitly (change plus per-day, per-week, per-30-day rates). Units, date format and the no-reference-comparison boundary are all stated, so an agent can invoke and interpret this correctly.

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%, including the detailed locale rationale, so the schema already carries parameter meaning. The description restates units (grams, cm, YYYY-MM-DD dates), which mostly duplicates the enum and format descriptions rather than adding syntax or ordering semantics. 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?

States a specific computation on a specific resource ('how fast a child grew between two measurements') and enumerates the outputs it produces. The closing clause 'does not compare it with a reference' cleanly separates it from growth_percentile and growth_trend among the siblings.

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?

Gives concrete triggering utterances ('how many grams a day is my baby gaining', 'how many cm did my child grow') and an explicit exclusion ('does not compare it with a reference'). It stops short of naming the sibling to use instead for reference-based comparisons, so routing is implied rather than spelled out.

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