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

The annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds real behavioral context beyond that: every response may carry serviceAnnouncements from Geekist, and each message must be shown distinctly to the user. It does not describe pagination or the shape of the hydration totals themselves.

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 sentences: the capability comes first, then the required response handling. Both earn their place and nothing is padded, though the announcement directive could be tightened slightly.

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?

For a read-only, two-parameter history tool with fully described parameters and no output schema, the description covers purpose plus a notable response-content obligation. Only the shape of the returned hydration totals and any pagination behavior are left unstated, which is minor here.

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 description coverage is 100%, and both startDate and endDate are documented with format and date-pattern constraints. The description only restates that a date range is involved and adds no syntax or boundary meaning beyond the schema, so the baseline of 3 applies.

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 a specific verb and resource: read daily hydration totals over a date range. That clearly separates it from sibling history tools like garmin_get_sleep_history or garmin_get_steps_history, but it never explicitly contrasts itself with an alternative tool.

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?

It implies usage through 'across a date range' but gives no explicit when-to-use, when-not-to-use, or prerequisite guidance. The second sentence is a post-call display instruction, not selection guidance, so an agent still has to infer when this tool is the right choice.

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