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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and non-destructive, so safety is covered. The description adds genuinely useful non-annotation context: the Open-Meteo sea level model as source and that heights are relative to mean sea level, plus a forecast horizon. It does not cover rate limits, timezone of the times, or refresh cadence.

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?

A single front-loaded sentence with no filler; the model source and datum are packed into a parenthetical. Efficient, though the parenthetical slightly buries operational info.

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 simple two-parameter read-only forecast with no output schema, the description covers what the data is and its reference datum. The gap is the input side: neither parameter's expected format or limits are conveyed, leaving the agent to guess at the resort identifier.

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 0%, so the description must compensate, and it largely does not. 'resort' is never explained (what form of name/ID?), and the 'days' parameter is only alluded to as 'the next days' with no mention of the 1-7 maximum enforced by the schema.

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: high/low tide times and heights at a beach resort, with a forecast horizon. It is clearly distinguishable from siblings like beach_conditions or sargassum_forecast, though it does not name any sibling explicitly.

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?

No when-to-use guidance, no exclusions, no pointer to alternatives. Usage is only implied by the tide/forecast framing; an agent gets no help deciding between this and beach_conditions for coastal info.

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