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

Annotations already establish read-only, idempotent, non-destructive behavior, and the description adds substantial behavioral context beyond that: default date handling, range semantics, the fact that tides only exist for coastal ports, and that freshwater requests return only moon phase and bestWindows. This is exactly the kind of runtime behavior an agent needs to know.

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 description is compact and front-loaded: it states the tool's output first, then usage triggers, then parameter defaults, then the important freshwater caveat. Every sentence carries useful information with no filler or repetition.

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 read-only tool with 7 optional parameters and no output schema, the description covers the main invocation scenarios, date/range semantics, and the freshwater exception. The main gap is the absence of the exact return structure, though the description does enumerate key returned data fields (tide table, moon phase, windows, water temperature, weather).

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%, so the schema already documents all 7 parameters. The description adds extra meaning by explaining date/range behavior and the freshwater fallback ('para água doce a ferramenta devolve a fase da lua e as janelas de horário do dia (bestWindows)'), which goes beyond the schema's parameter-level details.

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 starts with a concrete resource and payload: 'Condições de pesca de um dia: tábua de marés, fase da lua, melhores janelas de horário, temperatura da água e tempo.' It also ties the tool to specific user intents (maré, lua, melhor horário para pescar, se o dia está bom), making it easy to distinguish from sibling tools that cover species, locations, equipment, and techniques.

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 gives explicit trigger conditions ('Use quando o usuário perguntar sobre maré, lua, melhor horário para pescar, ou se o dia está bom') and explains date/range usage ('Hoje por padrão; passe date para amanhã... e range para a semana ou o mês inteiro'). It does not name an alternative tool or give an explicit 'when not to use', but it does describe the coastal vs freshwater boundary clearly.

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