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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered. The description adds genuine behavioral context beyond them: the water/pegel section is conditional on the water module being active, the 15 km radius is disclosed, and it states this is not an official warning and that the data source plus license must be cited from the summary.

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 aggregate scope before the disambiguation and examples; each sentence carries information (parts returned, sibling routing, caveat, citation duty). It is on the long side and the example questions add bulk, but nothing is redundant.

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, so the description must explain the return value — and it does, enumerating all returned components and the 15 km / 3h / 24h bounds, plus the conditional water section and the citation requirement. An agent has everything needed to call and interpret it.

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%, so baseline is 3, but the description adds domain meaning the schema does not: the value must be an Austrian municipality, and the 'wenn das Modul Wasser aktiv ist' framing clarifies what the single lookup feeds into. This modestly exceeds the schema baseline.

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 (aggregate overview) plus resource (Austrian municipality situation) and enumerates exactly what is bundled: current weather, 3h nowcast, 24h forecast, and optional nearby gauges. It explicitly names the sibling detail tools it is not, so it is distinguishable without opening any schema.

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 an explicit routing rule — use wetter_prognose, niederschlag_jetzt or pegel_in_der_naehe for details — and adds three concrete example questions showing the intended broad-overview use case. When-to-use and when-to-use-something-else are both covered.

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