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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds specific calculation details—sidereal orbital periods from NASA and Julian year for Earth—which helps the agent understand the data source and calibration. This is valuable beyond annotations, so a 4.

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 concise sentences deliver the core functionality and calculation basis without unnecessary words. Front-loaded with the operation.

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 a simple conversion, full schema coverage, a read-only annotation, and an output schema, the description suffices. It covers the essential context (source and Earth year definition) without needing to explain return values.

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?

The input schema has 100% coverage for the single parameter, describing bounds and data type. The description reiterates that age is in Earth days but adds no new parameter-specific details. Baseline 3 is appropriate.

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 clearly states the tool converts an Earth-day age to planetary years using a specific verb ('return') and resource (eight planets plus Pluto). It distinguishes from the sibling 'weight-on-other-planets' by focusing on age rather than weight.

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?

The description implicitly defines the use case: converting an age in Earth days to planetary ages. It does not explicitly name alternatives or exclusions, but the input-output relationship is unambiguous, and among siblings only this tool handles age conversion. A score of 4 reflects clear context without explicit alternative guidance.

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