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

Annotations already cover safety (readOnly, idempotent, non-destructive) and openWorld, so the bar is lower. The description adds genuine behavioral context beyond annotations: the unit system (ft, kt, s, F, mi), that directions are FROM, and that output includes source/freshness metadata. It omits any rate-limit or pagination behavior but is solid otherwise.

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?

Two compact segments, front-loading the core purpose before the units block. Every sentence carries information; nothing is padded, though the units line is dense.

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 appropriately discloses the return shape ('data and source/freshness metadata') and the unit conventions. Combined with the annotation coverage this is nearly complete, with only the spot parameter's format left unexplained.

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% and there is one required nested parameter (spot). The description only restates 'for a spot' without clarifying the identifier format, valid sources, or the meaning of the spot value, so it fails to compensate for the schema gap.

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: 'Actual buoy and station observations for a spot with timestamps'. It also implicitly contrasts itself with forecast tools ('may differ from blended forecast conditions'), helping distinguish it from siblings like get_forecast/get_conditions. It does not name a specific sibling, so it stays just short of 5.

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 phrase 'These may differ from blended forecast conditions' implies this tool should be used when actual measured data is wanted rather than a forecast, but no explicit when-to-use rule or named alternative is given. Usage must be inferred from the forecast contrast.

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