get_fitness_age_data

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds no behavioral context such as data freshness, whether the metric is computed or stored, or what the response contains. It does not contradict the annotations, but it adds essentially nothing beyond them.

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 extremely concise, with no wasted words, and the scope is front-loaded. It is a fragment rather than a structured sentence, but it is appropriately sized for a simple one-parameter getter.

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 simple read-only tool with one fully documented parameter, the description is minimally sufficient to invoke correctly. However, with no output schema and no explanation of what 'fitness age' represents or what fields are returned, it leaves a gap that a slightly fuller description could close.

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%: the single required parameter cdate is documented as 'Calendar date, YYYY-MM-DD (UTC)'. The description's phrase 'for one date' aligns with the schema but adds no syntax or format detail beyond it, so the baseline of 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 states a specific resource ('fitness age') and scope ('for one date'), which is enough to distinguish it from sibling tools like get_activities or get_sleep_data. It lacks an explicit verb, but the tool name supplies 'get', and the metric is unambiguous.

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?

There is no guidance on when to use this tool versus alternatives, nor any exclusions. It does not say whether a range-based sibling exists, whether this is suitable only for a single known date, or what to do for multi-date queries.

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