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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered and the bar is lower. The description still adds real behavioral context beyond them: a 50-facility cap, out-of-service equipment listed first, the guarantee that summary counts cover all facilities so a short list never hides a broken lift, and an attribution line on results. Ambiguous station names producing a disambiguation list ('the result lists them and asks which; do not guess') is a genuinely useful behavior disclosure, though nothing is said about failure modes when a station has no facility data.

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 front-loaded with the core purpose, then usage triggers, then the exclusion. It is long, but each sentence does work — the bilingual examples exist to route non-English queries and the exclusion prevents misrouting to departures. The clause about attribution lines is slightly marginal, keeping it off a 5.

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 return-value burden and does so: it lists the per-facility fields (location, state, operator explanation), the ordering rule, the cap, and the attribution line. Combined with annotations covering the safety profile and a 100%-covered schema, an agent has everything needed to call it correctly.

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 description coverage is 100% and the parameter descriptions are unusually thorough, so the baseline is 3. The description only echoes the limit semantics ('At most 50 facilities, out-of-service ones first') already spelled out in the limit field; it adds no new meaning for eva_no, station, facility or language beyond what the schema already documents.

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 specific verb and resource ('Report whether the lifts and escalators ... are working now') and enumerates exactly what is returned: each facility, its location, its state (in service / out of service / unknown) and the operator's explanation. It also distinguishes itself from the nearest sibling by name ('Do NOT use for train times, platforms or delays — call get_train_departures'), so an agent can separate it from get_departures without opening a 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?

Explicit when-to-use triggers are given with multilingual user phrasings ('Funktioniert der Aufzug am Kölner Hauptbahnhof?', 'Rolltreppe am Neumarkt kaputt?') plus the intent vocabulary that should route here: wheelchair, pram, heavy luggage, step-free access. An explicit exclusion and named alternative (get_train_departures) covers the main confusion case, leaving nothing to inference.

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