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 genuinely new behavior beyond the annotations by disclosing the validation contract: it throws GarminError when start > end, telling the agent this is an error rather than an empty result. It still says nothing about pagination or return shape, keeping it short of a 5.

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 short sentences, zero filler. The resource and range are front-loaded and the failure condition follows immediately.

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 read-only tool with a fully documented schema and no output schema, the description covers what is returned (max metrics such as VO2 max) and the one failure mode. Only the return structure/pagination is left unspecified, which is a minor gap for a read tool whose annotations already cover safety.

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 both date parameters carry format and UTC guidance in the schema, so the baseline is 3. The description's only added parameter meaning is the start > end ordering constraint, which is useful but minimal.

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+resource (max metrics / VO2 max values) plus scope ('over a date range'), which implicitly distinguishes it from the sibling get_max_metrics for a single point in time. It never names that sibling explicitly, so the differentiation is inferable rather than stated.

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 date-range scope implies when to reach for this tool versus a single-day variant, but there is no explicit when-to-use, when-not-to-use, or named alternative. An agent must infer the routing decision from the phrase 'over a date range' alone.

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