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

Annotations already establish readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context beyond that: it is pure arithmetic with no clinical interpretation, and it specifies the input unit convention (grams only, 3400 not 3.4), which is a real invocation trap.

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 the core definition, then use-case phrases, then the scope caveat, then the unit constraint — a sensible ordering with little waste. The example-query list is slightly repetitive, keeping it short of maximal efficiency.

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 compensates by naming all three returned values. For a four-parameter, read-only arithmetic tool whose annotations carry the safety profile and whose schema fully documents parameters, nothing an agent needs in order to call it correctly is missing.

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% and the locale param even carries its own detailed rationale, so the baseline is 3. The description pushes past baseline by reinforcing units for birthWeightG/currentWeightG and by describing the computed outputs (grams, percent, at/above birth weight), which the schema cannot convey since there is no output schema.

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 precise computation: the delta between a baby's current weight and birth weight, in grams and percent, plus regaining status. This is clearly distinguishable from siblings like growth_percentile, growth_velocity, and growth_trend, which track growth against references rather than a birth-weight baseline.

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 three concrete user phrasings that should trigger it ('how much weight has my newborn lost', 'newborn weight loss percentage', 'has my baby regained birth weight'), which is strong positive routing. It also adds a scope exclusion ('does not say whether the change is expected'), but never names an alternative sibling tool for the adjacent questions an agent might confuse it with.

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