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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds genuine behavioral context: the requirement dynamically rises on workout days, the glass size comes from Settings > Water, and a Cotlet API key with app access is required. That auth and dynamic-requirement detail is value beyond the structured fields.

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?

The first sentence is a fragment that largely restates the fuller second sentence ('Returns the water you logged for one day'), producing redundant content. Front-loading is reasonable but roughly a third of the text is duplicative.

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 correctly explains the return contents (logged water, computed requirement, glass size) and adds the auth requirement, which is what an agent would otherwise be missing. Minor omission: no mention of units (e.g., ml vs glasses) for the returned values.

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 the date parameter already documents format and the 'default: today' behavior, so the description adds little on parameters. Baseline 3 is appropriate when the schema carries full parameter meaning.

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 verb (get) and resource (water) and enumerates exactly what comes back: logged water for a day, daily requirement, and glass size. This distinguishes it cleanly from siblings like fitatu_get_daily_goals, fitatu_get_diary, and fitatu_get_nutrition_summary.

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?

The description implies the use case (reading a day's water data plus targets) but never says when to reach for this tool versus related ones like get_daily_goals or get_diary. No exclusions or prerequisites for choosing it are stated.

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