Get Garmin hydration

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds genuinely non-obvious behavior: data may be absent unless the user logs it, the default span is 7 days, and calls are capped at 31 days. Units (ml) are also disclosed, which structured fields do not convey. It does not describe the response shape (e.g., one entry per day, zero-filled vs omitted days), which is why it is not 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 dense sentences with zero filler: the first front-loads what the resource is and lists the payload fields, the second carries the caveats. Every clause earns its place.

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, the description compensates by naming the four returned metrics and their unit, plus data-availability and window limits, which is most of what an agent needs. The only shortfall is not stating the per-day granularity/shape of the response or how missing days appear.

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 carry their own date-format pattern and default rules. The description's 'defaults to the last 7 days; at most 31 days per call' restates what start_date and end_date already document, adding no new meaning about parameter interaction or time-zone handling beyond the schema. Baseline 3 is appropriate.

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?

Names a specific verb+resource ('Hydration per day over a date range') and enumerates exactly what is returned: intake, goal, estimated sweat loss, and activity intake in ml. That field list distinguishes it cleanly from siblings like garmin_get_steps or garmin_get_food_log without opening any schema.

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?

Gives a clear precondition ('Only has data if the user logs hydration') and windowing rules (defaults to last 7 days, max 31 days per call), which tells the agent when the tool is worthwhile and how far back it may reach. It stops short of naming an alternative sibling when the user wants a different wellness metric, so it is clear context rather than explicit routing.

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