wx_icon_d2

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

With no annotations provided, the description carries the full transparency burden. It discloses a key behavioral trait: fallback to lower-resolution models outside ICON-D2 coverage. It also lists output variables and model resolution, but omits details like return format, units, or error behavior. Still, it provides substantial insight beyond the bare tool name.

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?

The description is concise and well-structured: three sentences cover purpose, variables, model coverage, and fallback behavior. Every sentence contributes meaningful information, with the key action front-loaded in the first sentence.

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?

The description covers the essential context: coverage area, resolution, forecast horizon, output variables, and fallback behavior. No output schema exists, so the description appropriately communicates what the user receives. It could mention output format or units for full completeness, but the provided details are sufficient for a forecast tool at this complexity.

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% for all three parameters (lat, lon, hours), with clear descriptions in the schema. The tool description adds context about what the forecast includes but doesn't elaborate on parameter units or formats beyond the schema. Since the schema does the heavy lifting, a baseline of 3 is 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?

The description clearly states the tool's purpose: 'Get DWD ICON-D2 NWP forecast for any lat/lon.' It enumerates the specific weather variables (hourly wind, visibility, cloud base, precipitation, CAPE) and model characteristics, distinguishing it from sibling tools like wx_metar or wx_taf which are observational reports.

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 description gives clear context: ICON-D2 covers Central Europe at 2km resolution up to 48h, with a fallback to ICON-EU or ICON-seamless outside coverage. This tells users when to use the tool and what to expect based on location, though it doesn't explicitly name alternative tools for other forecast needs.

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