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

Annotations already cover readOnly/idempotent/openWorld/non-destructive, and the description adds real behavioral context: missing models are not synthesized ('absent models stay unavailable'), directions are FROM, units are fixed, and source/freshness metadata is returned. It stops short of describing the per-model return structure, which would be valuable with no output schema.

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 tightly packed sentences, purpose front-loaded and the units/direction convention grouped into a single compact clause. No filler, though the 'Units:' / 'Returns...' fragments read slightly telegraphically.

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 data fetch with no output schema, the description covers the essentials: what is returned (model series, spread, source/freshness metadata), units, direction convention, and partial-availability behavior. The only gap is the shape of the returned series per model.

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 the nested query.spot has only a regex/length constraint, so the description must carry the burden. It says only 'for a spot', giving no hint whether the value is a name, slug, or ID, nor any format guidance beyond the constraint pattern.

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 resource — 'Published wave-model series and model spread' — with the scope limiter 'for a spot', and the title reinforces the comparison intent, distinguishing it from the single-model get_waves. It never names get_waves as the alternative, so differentiation relies on the agent inferring 'model spread' means multi-model.

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?

There is no explicit when-to-use or when-not-to-use guidance; the comparison purpose is only implied by the title and the phrase 'model spread'. A user wanting a plain forecast vs. a multi-model comparison gets no routing help among the many forecast siblings.

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