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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The only behavioral addition is 'from any one known measure', which tells the agent at least one value is needed despite an empty required list — useful but minimal, with no mention of error behavior or precision.

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?

A single compact clause with no filler, front-loading the resource and the computed quantities. It is terse to the point of being slightly under-specified, but nothing is wasted.

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 an output schema present the return values need no explanation, and annotations cover safety. However, the 'calculation' selector (default 'all') and the zero-input edge case are unaddressed, leaving a handful of invocation questions the agent must infer.

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 coverage is 100%, so the schema already documents all five parameters. The description echoes four of them (area, circumference, radius, diameter) but ignores the 'calculation' selector parameter, so it adds essentially no meaning beyond the schema — baseline 3 applies.

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 names the concrete resource (circle) and the exact outputs (area, circumference, radius, diameter), so an agent knows this is the circle-geometry tool. It doesn't explicitly distinguish itself from near-neighbors like calculator_area or calculator_square, but the word 'circle' does the disambiguation.

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?

'From any one known measure' implies the calling pattern: supply one input and it derives the rest. There is no explicit guidance on when to pick this over calculator_area or calculator_geometry_3d, and no note on what happens if no measure is supplied (required list is empty).

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