Hydration

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

Adds substantial context beyond annotations: the pass-through nature of the data ('as Garmin returns it'), the high likelihood of empty results and how to interpret them, and the 92-day cap. Annotations already cover read-only/idempotent safety, so this is additive. It does not describe response shape or error behavior.

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?

Front-loads what the tool returns, then the empty-result caveat, then the range mechanics. Efficient, though the empty-result explanation takes two clauses that could be trimmed 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 simple 3-param read tool with no output schema, the description covers interpretation caveats and range mechanics well. Minor gap: no note on how empty days appear in the returned series (omitted vs. zero-value).

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 baseline is 3. The description adds the mutual-exclusivity pattern (period vs. start_date/end_date), the 92-day cap, and example period values, which is genuinely useful beyond the schema's own notes.

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?

States a specific resource and scope: 'Water intake the user logged in Garmin Connect, day by day over a range, as Garmin returns it.' It also distinguishes itself from get_daily_summaries, which is named as an alternative carrier of hydration_ml.

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?

Explains the key interpretation caveat (usually empty; empty means nothing was logged, not zero intake) and names an alternative source (get_daily_summaries hydration_ml). It also explains how to specify the range. It lacks an explicit 'prefer X when' routing sentence, but the alternative mention gives clear context.

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