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

Annotations cover safety metadata (readOnlyHint=false, openWorldHint=true, idempotentHint=false), and the description adds material context beyond them: the data provenance (Norwegian Meteorological Institute) and, critically, the x402 payment model at $0.002 USDC on Base per successful call — a cost/auth detail an agent must know before invoking. It still omits failure behavior, rate limits, and whether the forecast horizon changes cost.

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 retrieval method, and the field enumeration is informative rather than filler since there is no output schema. The trailing list of use domains and pricing sentence are slightly padded but each carries real decision value, so only minor trimming is possible.

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 takes on the burden of describing returns and does so thoroughly (every returned field plus forecast length). Parameters are fully documented by the schema and payment is disclosed; only error/edge behavior and output units for wind are missing, which is a small residual gap.

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 coverage is 100% and every parameter carries a description with range and default ('lat -90 to 90', 'lon -180 to 180', 'hours 1-48, default 12'), so the schema carries the semantics. The description only restates the 48-hour forecast ceiling and otherwise adds no parameter nuance, making the baseline of 3 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 resource and access path ('Weather for any point on Earth by latitude and longitude') and then enumerates exactly what is returned — temperature in Celsius, conditions, precipitation, wind, humidity, cloud cover, pressure, plus an hourly forecast up to 48 hours. Nothing about the tool's function is left ambiguous, and it is unmistakably distinct from every sibling (base-gas, fx, time, etc.).

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 explicit use contexts ('travel and event planning, logistics, agriculture') and a catch-all for any agent needing weather, which is clear guidance for when to reach for it. It offers no exclusions or named alternatives, but none exist among the siblings, so the only real gap is minor.

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