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), so the bar is lower, and the description adds real value beyond them: it explains what band crossings mean clinically (one is common while a child settles onto their own curve; two downward is the pattern clinicians review) and discloses a scope limitation about velocity standards.

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 the tool reports, then adds the interpretive note on crossings, then the scope limitation. Three sentences, each carrying information, with no filler or repetition of the title/annotations.

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, so the description carries the burden of describing return content, and it does enumerate the returned components (percentile and z-score per point, positional shift, count of crossings). It stops short of defining the exact output shape or field names, leaving a small gap for a nested-input, multi-output tool.

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 high (83%), so the schema already documents sex, locale, standard, and the age/value fields, including corrected-age guidance. The description adds no syntax, format, or default details beyond what the schema provides, so the 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 verb and resource: what moved between two measurements, listing the concrete outputs (percentile and z-score at each point, position shift, band crossings). It explicitly distinguishes itself from the sibling growth_velocity by declaring that WHO Growth Velocity Standards are not implemented and that it never claims a percentile for rate of gain.

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 clear context for when the tool applies (comparing two attained-growth measurements) and explicitly carves out the velocity-percentile use case as out of scope, which implicitly routes that request to growth_velocity. It stops short of naming the alternative tool or stating required prerequisites, so it is not a full when/when-not/alternatives treatment.

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