add_weigh_in

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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description does add genuine behavioral facts beyond the annotations: the unit defaults to kg and the timestamp defaults to the current moment. It does not disclose what happens on a duplicate weigh-in for the same day, which matters for a mutation tool.

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?

Very short and free of filler, so nothing is wasteful, but it is a sentence fragment with no front-loaded purpose statement. Brevity here comes from omission rather than from efficient editing.

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?

A mutation tool with no output schema, 33% schema coverage, and no usage guidance leaves real gaps: no statement of purpose, no sibling differentiation from `add_weigh_in_with_timestamps`, and no note on duplicate handling. The defaults alone are not enough to call it complete.

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 only 33% (only `when` is documented in the schema), so the description must compensate. It does so partially by giving the default `unitKey="kg"` and `when=new Date()`, which clarifies the enum default and the optionality. `weightValue` remains undocumented in both places, including the unit it is expressed in.

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 never states what the tool does; it only supplies default values for two optional parameters. The purpose must be inferred entirely from the name `add_weigh_in`, which is exactly the tautology-adjacent case the rubric penalizes.

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 when-to-use guidance and no mention of the obvious alternative, `add_weigh_in_with_timestamps`, which appears in the sibling list. The `when=new Date()` default faintly implies 'use this when you don't supply a timestamp', but that distinction is left for the agent to reconstruct.

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