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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the safety profile is covered. The description adds genuine unannotated traits: a hard cap of five spots, sampled-stops-only semantics, the exclusion of depth/bridge/zone checks, the unit conventions, and the presence of source/freshness metadata in the response.

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?

Three tight sentences, front-loaded with the primary capability, followed by scope exclusions then units. Every clause carries information; nothing is restated from the title or annotations.

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?

No output schema exists, but the description discloses what comes back (conditions data plus source/freshness metadata), which is what the agent needs most for a nested-param read tool. The only residual gap is the exact encoding of the 'spots' string, which is neither in the schema nor fully resolved here.

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 single nested 'spots' string param is undocumented in the schema, so the description must compensate. It does add key meaning ('up to five ordered spot IDs'), but it never states the encoding of the string — separator, ID format, or how the 500-char maxLength maps to five spots — leaving real ambiguity for a 1-param tool.

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 ('Weather and marine conditions at up to five ordered spot IDs') and immediately scopes it against the adjacent capability ('does not create a navigable route'). An agent can distinguish this from plan_route/plan_my_route without opening the schema.

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 context (sampled stops, up to five, ordered) and explicit exclusions (no depth, bridges, zones, or conditions between stops), which tells the agent when this tool is the wrong choice. It never names the alternative tool by name, so routing relies on inference from the negative scope rather than an explicit 'use X instead'.

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