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

Beyond the readOnlyHint/openWorldHint annotations, it discloses real behavioral traits: no observed range limit (1000 days answered), a reversed range throwing before any request even though Garmin accepts one, and the response envelope ({userGoals, userGoalRanges}) with units. This is exactly the kind of edge-case context annotations cannot convey, though error/permission behavior beyond the reversed-range case is not covered.

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?

It is compact and front-loads what the tool returns before the endpoint and caveats. Some density comes from internal identifiers ('PersonalApi.UserGoalsRangeDTO', the raw path), which are less useful to an agent than the behavioral facts, but no sentence is filler.

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?

With no output schema and only two simple params, the description covers return shape, units, range behavior, and a failure mode — enough to call it correctly. The main remaining gap is not distinguishing it from get_goals, which shares the 'goals' concept and could cause misselection.

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%, so date formatting is already documented. The description still adds meaning the schema cannot: the ordering constraint on start/end (reversed range throws) and that the returned weights are in grams, not user units.

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 first sentence gives a specific verb and resource ('The weight goals in effect between two dates, in grams') and pins the time window, so an agent knows exactly what it retrieves. It never references the nearby sibling get_goals, which also covers goals, so the boundary between the two is left for the agent to guess.

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 only implied by the date-range framing; there is no explicit statement of when to call this versus get_goals, get_weigh_ins, or get_body_composition. The reversed-range note is a calling constraint rather than guidance on tool selection.

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