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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds traits they cannot carry: no per-line granularity, a hard 120-minute window cap, region-level data filing (a town is reported as its Kreis and the answer says so), and mandatory licence attribution (CC BY-SA DELFI / CC BY 4.0 VBB). These are real operational constraints an agent must respect.

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 purpose and tightly packed, with the when/when-not routing and the licence clause each doing work. The parenthetical German query examples add length but also real disambiguation value, so only minor trimming is possible.

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 burden and does so — it names the four reported metrics and the alert types (diversions, closed stops). Zero required parameters plus documented lat/lon-vs-region exclusivity and the language default warning cover 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%, so the baseline is 3; the description largely restates the window limit ("Window ≤ 120 min") already documented in the schema. Its genuinely additive notes — no per-line figures and the lat/lon vs region exclusivity — are already covered by the parameter descriptions, so it does not meaningfully extend parameter semantics.

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 resource (punctuality of public transport in one German region) and enumerates exactly what is reported: share of trips >5 min late, cancelled stops, trend, and service alerts in force. It explicitly separates itself from get_train_departures and rules out per-line figures, so an agent can distinguish it from siblings without opening the schemas.

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 positive trigger ("Use when asked whether buses and trains run normally, or a strike, storm or works disrupt them") and an explicit negative one ("Do NOT use for a station's departures or a line from a named DEPARTURE station... get_train_departures"). The German example even disambiguates a destination phrase ("nach …") from a departure station, which is unusually precise routing guidance.

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