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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds real behavioral context: units per metric, the date format, and the explicit limitation that no reference comparison is performed — which matters because the sibling tools do compare against references. It does not mention the disclaimer/clinician note that the locale parameter implies.

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?

Three sentences, front-loaded with the computed output and followed by usage examples and unit conventions. Each sentence carries information; only the unit/date restatement duplicates the schema slightly.

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?

There is no output schema, and the description names the returned quantities (change, per-day, per-week, per-30-day rates), which is enough for an agent to relay results. The only gap is that the returned disclaimer/clinician note, hinted at by the locale parameter, is never described.

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%, with metric units, date format and positivity bounds all documented in the schema itself. The description restates the unit conventions and date format but adds no syntax or edge-case detail beyond that, so 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 states exactly what is computed: the change between two measurements plus rate per day, per week and per 30 days. It also differentiates itself from the percentile/reference siblings by saying it 'states the rate and does not compare it with a reference', so an agent can place it against growth_percentile, zscore_percentile and growth_trend.

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?

It gives concrete user-phrasing triggers ('how many grams a day is my baby gaining', 'how many cm did my child grow') and a scope exclusion (no reference comparison). It stops short of naming an alternative sibling tool for when a percentile comparison is what the user actually wants.

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