get_body_weight

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

With no annotations, the description carries the full burden of behavioral disclosure. It does not explicitly state that this is a read-only operation, nor does it explain what happens when 'day' is omitted or null, what timezone applies, or how missing data is represented. The listed metrics provide some context but not sufficient behavioral detail.

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 a single, front-loaded sentence with no filler. It efficiently conveys the core resource and a few key output metrics. It could be slightly clearer with an explicit verb, but it is appropriately concise for a simple 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?

There is no output schema and no annotations, so the description should provide a fuller picture. It partially describes the return values (grams, BMI, body fat) but leaves 'etc.' undefined and fails to clarify behavior when 'day' is absent. For a tool with a single optional parameter, this is a notable gap that could lead an agent to call it incorrectly.

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 provides no descriptions, so the description must compensate. It does add the crucial YYYY-MM-DD format for the 'day' parameter, which is meaningful. However, it does not explain the semantics of the default null value or whether omitting the parameter returns the latest available weight, leaving part of the parameter's meaning undocumented.

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 identifies the resource (body weight) and scope (a single day with YYYY-MM-DD format), and lists key returned data (grams, BMI, body fat). While it lacks an explicit verb like 'Gets', the tool name and context make the action clear, and the single-day scope distinguishes it from the sibling get_weight_history.

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?

No guidance is provided on when to use this tool versus alternatives such as get_weight_history or get_weight_goal. The 'for a day' phrasing implies single-day usage, but there is no explicit when/when-not statement or mention of the alternatives, leaving the agent to infer the routing.

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