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

Annotations already declare readOnly, idempotent, open-world and non-destructive, so the safety profile is covered. The description adds genuinely new behavior: a regional coverage limit (Nordic and North Sea waters) and a pricing model (free within daily allowance, then $0.002 USDC via x402), both of which affect whether an agent should call it.

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 sentences, zero filler, and the data/resource statement is front-loaded ahead of the pricing caveat. Every sentence carries distinct information.

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?

An output schema exists, so return-value detail is not required, and annotations carry the safety profile. The description covers geographic scope and cost, leaving only minor gaps (coordinate format, units) that the schema partially handles.

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% with only lat/lon, both documented in the schema, so the baseline is 3. The description adds no coordinate format, unit, or valid-range detail beyond what the schema already states.

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?

The description names a specific resource set (wave height and direction, sea temperature and currents) and scopes it to Nordic and North Sea waters, which cleanly separates it from global-weather__forecast and global-weather__moon/sun. It states clearly what data comes back but never names a sibling to route against.

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 when-to-use guidance and no mention of when an agent should prefer global-weather__forecast or any other sibling over this tool. The geographic scoping is the only implicit selection hint, and it is not framed as a usage rule.

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