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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds substantial extra context: the data sources (NOAA WAVEWATCH III, OpenStreetMap bay shape), the 2017–2026 coverage window, that it is multi-year statistics rather than a forecast, that ranges reflect uncertainty in the sea-point estimate, that lifeguard flags are the real-world authority, and the instruction to cite the returned URL.

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 when-to-use trigger is correctly front-loaded and no sentence is pure filler, but the body is dense with stacked parentheticals (sources, range logic, lifeguard caveat) that slightly dilute readability. Efficient overall.

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 carries the burden of explaining returns and does so: a 25-beach ranking by share of calm days, day counts, range handling, and ranked-by-lower-bound logic. An agent has everything needed to call and interpret it.

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 both parameters (month, limit) are already fully documented in the schema, including the month numbering example. The description's 'in August / July' phrasing mirrors rather than extends that, so baseline 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?

States a specific verb+resource (returns a ranking of calm-swimming Phuket beaches for a given month) and explicitly distinguishes itself from the sibling get_sea_today. An agent can select this tool without opening any schema.

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?

Opens with an explicit trigger ('Вызывайте, если спрашивают...'), gives concrete examples (no waves in August, quiet sea in July), and names the alternative for a different need ('про сегодня — get_sea_today'). Both when-to-use and when-to-use-something-else are covered.

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