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

Annotations already cover the safety profile (readOnly/idempotent/non-destructive), yet the description still adds substantive behavior: NOAA WAVEWATCH III source with 6-hour refresh, a hard freshness cutoff ('данные старше 12 часов не выдаются: ответ «нет свежих данных»'), the open-sea/bay-shape model caveat, the warning that lifeguard flags are decisive, plus inclusion of NOAA OISST water temperature and a citation 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?

Front-loaded with the trigger condition, then the return payload, then freshness and caveats – a sensible order. It is dense and runs long across several clauses, so some tightening is possible, but nearly every clause carries information.

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 return-shape burden and does so fully: wave class, wave height estimate, water temperature, data timestamp, URL, and the empty-result case ('нет свежих данных'). Nothing an agent needs in order to call and interpret it is missing.

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 single 'beach' parameter is fully documented there, so the baseline is 3. The description adds meaning beyond the schema by stating the output scoping: with the parameter you get one beach, without it all 25 – a behavioral consequence the schema does not express.

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?

Stated with a specific verb-and-resource framing: it answers 'where is the sea calm in Phuket today' and returns wave class, wave height, water temperature, data time and a URL for 25 beaches. The scope is unmistakable. However, it never names or distinguishes itself from the overlapping sibling get_calm_beaches (and get_weather_now), so an agent cannot tell which to prefer from the text alone.

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?

Explicit trigger conditions are given in the opening clause ('Вызывайте, если спрашивают, где... нет волн, на каком пляже сейчас спокойное море...') plus the English 'Call it for ...'. This is clear context for when to reach for the tool. It stops short of exclusions or naming alternatives, so it is not a 5.

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