Hydration

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

Annotations already declare readOnly, idempotent, non-destructive, openWorld, so the safety profile is fully covered and the description needn't restate it. The description does add one piece of genuine behavioral value absent from structured data and from any output schema: the result is bucketed per day and reported against a goal. It says nothing about units, defaults, or empty/missing-day handling.

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?

A single eight-word fragment with zero filler. It is compact, but the absence of a leading verb makes it read like a field label rather than an instruction, so it is slightly under-structured rather than optimally front-loaded.

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 two-parameter read tool with rich annotations, the definition is broadly sufficient and does hint at the return shape (per-day intake vs. goal) despite no output schema. However, an agent still cannot know the unit of measurement, what a day with no log entries looks like, or the maximum range allowed.

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% – start_date, end_date, format, inclusiveness, and the 'defaults to today' behavior are all documented in the schema. The description's phrase 'over a range' merely echoes that. Baseline 3 applies; no compensating detail is needed or added.

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 the specific resource (logged water intake) plus two distinguishing qualifiers: measured against a goal, aggregated per day, over a date range. That is far more specific than 'get hydration' and lets an agent tell it apart from get_daily_overview or get_food_log. It loses a point only because it is a verbless noun phrase that never says 'retrieves/returns'.

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?

There is no statement of when to use this tool versus the many sibling data getters (get_daily_overview, get_food_log, get_daily_summaries), nor any exclusion or prerequisite. Usage can only be inferred from the resource name and the date-range parameters.

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