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

No annotations are provided, so the description carries full responsibility. It lists the returned fields, which implies a read-only, deterministic operation. While it does not explicitly state safety or authorization needs, the nature of the calculation suggests low risk. The output structure is well-described, adding transparency.

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 concise, consisting of two sentences that efficiently convey the tool's function and output. The first sentence states the purpose and includes key details, and the second provides a helpful cross-reference. No wasted words.

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?

Given the simple parameter set (one required string), the existence of an output schema (implied by the description), and a large sibling list, the description is complete. It covers what the tool does, what it returns, and where to find related calculators. No gaps remain.

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 with a single parameter described as 'YYYY-MM-DD — Date of birth'. The description does not add further meaning beyond what the schema already provides. Since coverage is high, the baseline score of 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 calculates exact age in years, months, and days from a birth date. It specifies the verb 'calculate' and the resource 'age', and distinguishes itself from siblings by providing specific output fields and referencing related calculators via list_bundles.

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 includes a reference to list_bundles for related calculators, hinting at alternative tools like calculate_age_in_units, but it does not explicitly state when to use this tool versus others or provide contextual prerequisites. More guidance on when to use this precise age calculation would improve the score.

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