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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and closed-world behavior, so the safety profile is carried by structured data. The description adds the returned unit set, but since an output schema exists that is largely redundant, and nothing is said about date-range limits, future dates, or error behavior.

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 with the core operation front-loaded, and nothing is padded or vague. The middle sentence listing return units duplicates what the output schema already provides, which is the only wasted space.

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 one-parameter, read-only calculator with full schema coverage and an output schema, the definition covers what the agent needs to invoke it correctly. The remaining omission is sibling disambiguation against calculate_age, which the description leaves to inference.

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% and the single parameter 'birth_date' is documented as YYYY-MM-DD in the schema itself. The description only restates 'from birth date' without adding format, range, or edge-case meaning, so the baseline of 3 for a fully documented single-parameter tool 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?

States a specific verb and resource ('Calculate exact age in multiple units from birth date') and names the output units, so the operation is unambiguous. However, the sibling list contains a plain 'calculate_age', and this description never explains how it differs from that tool, which is the single most likely confusion an agent would face.

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 only guidance is 'See list_bundles for related "fun" calculators', which is a cross-reference to browsing, not a when-to-use rule. There is no statement of when to prefer this over calculate_age, calculate_pet_age, or calculate_dog_age, and no input prerequisites beyond the required birth_date.

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