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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered by structured data. The description's only added trait is the scope restriction to adult sizes; it adds no info on output shape, precision, or rounding, which is a modest contribution given the annotation coverage.

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 illustrative example, then the purpose, then a URL. Two sentences, no filler. The trailing web page link is promotional rather than functional and slightly dilutes an otherwise tight definition.

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 should clarify what the call returns (a single converted size, or all systems at once). The example implies a multi-system result but does not state it, so an agent cannot fully predict the response. Adequate but with a clear gap for a no-output-schema 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 100% and the enum already lists usM/usW/uk/eu/cm. The description adds value by expanding those abbreviations into readable system names and giving a concrete value example, but it does not explain the number range (1-60) or default behavior. Baseline 3 is appropriate when the schema carries most of the load.

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: 'Convert adult shoe sizes between US men's, US women's, UK, EU and Japanese cm.' The concrete example ('A US men's 9 is a UK 8.5, an EU 42.5 and 27 cm') makes the scope unmistakable and clearly separates it from generic siblings like unit_converter, height_converter, or cooking_converter.

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 a clear usage context: 'before you order from abroad,' which tells the agent when this tool is relevant. It does not, however, name an alternative (e.g., unit_converter) or state exclusions besides implying adult-only sizing.

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