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

With no annotations present, the description carries the full burden and does so unusually well: it discloses the data provenance (institute's own model run), that units are as the institute declares, and the commercial model ($0.01 per call via x402/USDC). Cost and payment method are exactly the kind of behavior an agent needs before calling and cannot get from structured fields.

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 usage trigger, then returns, then provenance, then price — a sensible ordering with no filler. The 'not an aggregator' clause is slightly editorial but it does convey a meaningful trust distinction, so it earns its place.

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?

There is no output schema, so the description must describe returns, and it enumerates temperature, humidity, pressure, wind speed/bearing, cloud cover, next-hour precipitation, plus model run and units. The main omission is how the 'hours' steps surface in the response and roughly how fresh 'now' is.

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 lat/lon/hours are already fully documented, which sets the baseline at 3. The description adds nothing about parameters and notably never mentions the 'hours' parameter, describing only 'the next hour's precipitation', which understates the 0–24 hourly-step capability in the schema.

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 concrete verb and resource — 'current conditions for any point on Earth' — and names the authoritative data source (MET Norway official model, explicitly 'not an aggregator'). An agent immediately knows this is a point-observation lookup. It does not name the sibling weather_forecast, so the now-vs-future split must be inferred from the word 'current'.

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?

'Use when an agent must act on the weather right now and be able to cite it' gives a clear, actionable trigger condition, including the citability requirement. It stops short of an explicit exclusion (e.g. 'for future days use weather_forecast'), so the alternative is only implied.

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