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

The annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false. The description adds valuable behavioral context beyond those annotations: free results cover US, UK, inside diameter, and circumference, while paid plans add Europe, Japan, Switzerland, and Australia, and it states a cost of 1 credit. It does not describe error handling or rate limits beyond the credit cost, so it falls short of a 5.

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?

The description is two sentences and front-loads the core conversion behavior before the paid-tier caveat. It is slightly redundant by repeating 'Ring Size Converter:' at the start, but otherwise every sentence adds useful information.

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?

For a simple three-parameter conversion tool with an output schema, the description covers purpose, free output fields, paid-region coverage, and credit cost. It could do more to explain the all-optional parameter set and how to choose between size and measurement, but it is broadly complete.

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 baseline is 3. The description hints at two input modes—'international ring sizes or millimeter diameters'—but does not clarify how the `from`, `size`, and `measurement` parameters interact, which one takes precedence, or what format `from` expects beyond the schema example.

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 a specific verb and resource: 'translates international ring sizes or millimeter diameters into US and UK standards, inside diameter, and circumference.' It is immediately distinguishable from siblings like ShoeSizeConverter or UnitConverter by the ring-size domain and the explicit output measurements.

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?

Usage is implied by the purpose statement—convert ring sizes or diameters—but the description offers no explicit when-to-use guidance, no exclusions, and does not name alternatives such as UnitConverter or ShoeSizeConverter. An agent can infer the basic use case but gets no routing help.

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