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

Annotations already cover read-only, idempotent, non-destructive and closed-world behavior. The description adds valuable operational context beyond that: severe acute malnutrition is flagged as urgent, and supplying a country makes the tool report which chart that country's health record uses. It does not discuss response format or error conditions, but the output schema exists.

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?

Two compact paragraphs: the first front-loads what the tool computes and its authoritative sources, the second immediately states the usage rule and the alternative. Every clause carries information, with no filler or redundant restatement of the name.

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?

Given a six-parameter tool with full schema coverage, an output schema, and rich annotations, the description supplies everything an agent needs: purpose, when to use it, alternative routing, country-chart behavior, and the urgent malnutrition flag. Return values are left to the output schema, which is appropriate.

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%, so the schema already documents each parameter thoroughly. The description still adds meaning by explaining the country parameter's chart-selection behavior and reinforcing that sex, age and at least one measurement are needed. It does not independently document all parameter constraints, but it goes beyond the schema baseline.

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: calculating where a child sits on growth charts from named WHO/CDC tables, covering weight, height, weight-for-height and BMI percentiles and z-scores. It distinguishes itself from siblings by naming paediatric_question_with_sources and contrasting arm-measurement malnutrition queries.

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?

Explicitly says when to use it: 'Use when you have a child's sex, age and weight or height and want the percentile.' It also names the alternative for malnutrition with an arm measurement and general growth questions, leaving no ambiguity about tool selection.

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