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

Annotations already declare this as read-only, idempotent, non-destructive, and closed-world. The description adds useful behavioral context beyond annotations: it cites reference gestation ranges and warns that 'a calendar cannot confirm pregnancy,' clarifying the tool's limits. It does not describe the exact return format, but the simple calculator nature makes that less critical.

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?

Three short sentences, front-loaded with the core calculation, followed by usage guidance and a limitation caveat. Every sentence adds value with no redundancy.

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 two-parameter calculator with annotations covering safety and no output schema, the description gives enough context to invoke it correctly. The only minor gap is that it does not explicitly state the shape of the returned planning window, though 'planning window' implies a date range.

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 50%, so the description needs to add meaning, and it does: it identifies both inputs (species and breeding date) and maps species to the relevant gestation ranges. The date format is already documented in the schema, so this is sufficient.

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: calculate a planning window from a known goat or sheep breeding date. It names the species and gives the Penn State gestation ranges, making it clearly distinct from sibling tools like dog_years_calculator or horse_weight_estimate.

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?

It explicitly says when to use the tool: 'Use when someone asks when a goat or sheep might kid or lamb.' That is clear contextual guidance. It does not name alternatives or exclusions, but the use case is distinct enough that this is a minor gap.

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