get_body_metrics

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description still adds genuine behavioral context the annotations cannot: missing fields are reported as 'not recorded' rather than zero, and results are informational rather than medical advice - both directly shape how an agent should interpret and relay data.

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 tight sentences, front-loaded with the metric list, then the date-range semantics, then the caveat. The only waste is the leading 'T8.' identifier, which carries no meaning for an agent choosing a tool.

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?

An output schema exists, so return values need not be spelled out, and the schema covers both parameters completely. Combined with a strong annotation set, the description supplies the one thing structured fields cannot - the 'not recorded' sentinel semantics - leaving little an agent would need that is missing.

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 100% and both parameters are fully documented in the schema, including the inclusive YYYY-MM-DD format and the 90-day cap, so the baseline is 3. The description does add one useful nuance - that 'end' is also the snapshot date for SpO2 and fitness age - but that is a small increment over the schema.

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 names the concrete resource contents - weigh-ins in kg, BMI, body fat, hydration, SpO2 and fitness age - over a date range, which is far more specific than a generic 'get body metrics'. It does not explicitly differentiate itself from siblings like get_daily_overview or get_account_status, but the enumerated fields make the scope 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?

Usage is implied by the content ('body metrics over a date range', 'as of the end date') rather than stated. There is no explicit 'use this when...' or 'use X instead for...' guidance against the eight sibling tools, so an agent must infer that this is the body-composition/SpO2 source rather than, say, the sleep or HR one.

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