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

Annotations already establish that this is a readOnly, idempotent, non-open-world operation, so the burden is low. The description adds genuinely useful output context — results are returned in litres, cups and ounces — going beyond the structured annotations, though it says nothing about how kg vs lb defaults interact.

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?

Three short sentences, front-loaded with a concrete example that quickly conveys scale before stating the actual capability. The trailing web page URL is mildly promotional but does not bloat the definition.

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 fills the gap by naming the returned units (litres, cups, ounces). For a simple stateless calculator with all-optional, fully documented params, this covers the essentials, though default behaviour (70 kg / 155 lb / metric / temperate / 30 min) is never surfaced in prose.

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%, so all five parameters are already documented, making 3 the correct baseline. The description corroborates the weight/exercise/climate inputs but adds no format, range or unit-selection detail beyond the schema, and never mentions the 'units' parameter.

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 and resource — 'Get your own daily target in litres, cups and ounces' — and even names the outputs and the inputs (weight, exercise, climate) that drive it. It clearly distinguishes itself from the many other health siblings like bmi_calculator or tdee_calculator.

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?

Usage is implied by 'from weight, exercise and climate', but there is no explicit when-to-use or when-not guidance and no routing to or away from any sibling. A user gets enough to know it estimates hydration, but nothing about edge conditions (e.g. selecting metric vs imperial).

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