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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld=false), and the description adds real context beyond them: the 7-day cap, the 30 km snapping radius, the inclusion of a data-quality field, and that access is free. It does not mention pagination or any failure mode when no covered spot is within 30 km.

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 resource and scope, then the input rule and cost in a short second sentence. The long comma-separated enumeration of return fields is somewhat dense and partly duplicates the output schema, but it is not padded or repetitive.

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?

Covers scope, date window, spot-vs-coordinate resolution, the 30 km fallback, and cost. With an output schema present, the return-value detail need not be in the description, and nothing needed to call it correctly 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 description coverage is 100%, so all five parameters are already documented, including the spot-OR-lat/lon exclusivity. The description restates the spot-vs-lat/lon choice and the nearest-spot rule, adding little syntax or format detail beyond the schema; baseline 3 is appropriate.

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 (get) and resource (ocean conditions) with explicit scope: facts for ONE covered spot over up to 7 days, enumerated as 3-hour forecast periods. The 'ONE spot' scope cleanly separates it from siblings like best_day and recommend_spot without needing to name them.

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?

Gives clear input-selection guidance ('Pass a spot id, or lat+lon to use the nearest covered spot within 30 km') and notes the tool is free, but never says when to prefer this over best_day or recommend_spot. Usage is implied by the fact-listing scope rather than stated.

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