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

With no annotations, the description carries the full burden and does disclose high-value operational facts: the data source (DMI Open Data) and the paid, metered nature (0.005 USD per call via x402). It omits failure behavior (no nearby station), units, and observation staleness, which matter for an unannotated tool.

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?

A single dense sentence leads with what the tool returns and how it is located, then tacks source and pricing on the end. No filler or repetition of the tool name.

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, and the description compensates by listing the returned measures (temperature, wind, gusts, pressure, precipitation, visibility). Cost is covered. The remaining gaps are unit conventions and the fact that all three parameters are optional, leaving the agent unsure whether an empty call is valid.

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%, but the lat/lon descriptions are just 'lat'/'lon', so the description adds real meaning by explaining they resolve to the *nearest* DMI station, and that station id is an alternative rather than a third filter. It does not say whether lat and lon must be supplied together.

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 and resource ('Latest observed weather in Denmark') plus the retrieval mechanism (nearest DMI station to lat/lon or a station id), and enumerates the returned measures. No sibling in the list offers weather, so the boundary is unambiguous.

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?

The 'latest observed' framing plus 'nearest DMI station to a lat/lon (or a station id)' implicitly tells the agent which input mode to use and that this is current conditions, not a forecast. It stops short of any explicit when-not-to-use guidance or note about what happens when no station is near the coordinates.

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