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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint, so the safety profile is covered. The description adds genuinely useful behavior: data refreshed at most hourly, a hard cap of 20 results sorted by distance, the explicit disclaimer that this is not an official warning, and the license attribution appended to the answer.

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 core purpose, output contents, freshness, caveat and examples are front-loaded in a compact block with no filler sentences. The example questions are the only slightly redundant element, but they earn their place as disambiguation aids.

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 fully specifies the return payload (per station: water body, value with unit, measurement time, low/mean/high flow stage, trend), plus result ordering, count limit, data staleness and the license footer. Nothing an agent needs to call this correctly or interpret the response is missing.

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% and both parameters (ort with its three accepted formats, radius_km with range and default) are fully documented in the schema itself. The description only alludes to the search area and the 20-result cap, adding nothing about parameter syntax or formats, so the 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?

The description names a precise resource (current gauge stations for water level or discharge from the Hydrographic Service), its scope (radius around an Austrian municipality), ordering (by distance) and cap (max 20), so the agent knows exactly what it returns. It does not explicitly name the nearest sibling, pegel_an_gewaesser, but the municipality-radius framing implicitly separates the two.

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 three example questions ("Wie hoch ist die Enns in Steyr?", "Welche Pegel gibt es rund um Schärding?", "Steigt das Wasser bei Hallein?") give concrete selection context, and "Keine amtliche Warnung" signals the boundary against a flood-warning tool such as hochwasserlage. No explicit when-not or named alternative is given, so it stops short of a 5.

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