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

Annotations already declare readOnly, openWorld and non-destructive. The description goes beyond them by disclosing the fallback behavior (stale nowcast yields hourly forecast values and the response says so), the license attribution footer, and the non-official-warning caveat. It does not mention rate limits or latency, but the added behavioral context is meaningful.

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 core capability, then fallback behavior, disclaimer, examples and license note. Slightly long due to multiple example questions, but every element (granularity, fallback, warning caveat) 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?

With no output schema, the description carries the burden of describing the result: 3-hour window at 15-minute steps, temperature/wind/gusts, forecast fallback, and a source/license trailer. That is sufficient for an agent to call and interpret it; only the exact output shape and field naming remain unspecified.

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?

Only one parameter ('ort') and schema description coverage is 100%, so the schema fully documents accepted forms (municipality name, optional state, five-digit GKZ, or coordinates). The description adds no syntax or format detail beyond the schema; baseline 3 applies.

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?

Specific verb+resource with scope: precipitation for the next 3 hours in 15-minute steps (GeoSphere Austria nowcast) for an Austrian municipality, plus temperature, wind and gusts. It is clearly distinguishable from wetter_prognose by its nowcast horizon and granularity, though it does not name that sibling explicitly.

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?

Example questions ('Regnet es gleich in Linz?', 'Wann hört der Regen in Graz auf?') give concrete usage context, and the disclaimer 'Keine amtliche Unwetterwarnung' signals when not to rely on it for warnings. However it never points to an alternative sibling (e.g. wetter_prognose or lage_am_ort) for those cases, so the routing guidance is incomplete.

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