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

With no annotations, the description carries the full burden and does well: it discloses that the data is real-time, that stop names are fuzzy-resolved to the best match automatically (so exact IDs are not required), and how timestamps are interpreted (local Berlin time when no zone). It still omits failure behavior for unresolvable names and any rate/auth constraints.

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?

Three dense sentences, front-loaded with the core action, then name resolution, then timing defaults. Every clause conveys a constraint or behavior; nothing is filler.

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?

For a 5-parameter read tool with no annotations and no output schema, the description adequately covers scope, resolution behavior, and time handling. It stops short of describing the shape of a returned journey or what happens when no stop matches, which leaves a small gap given the absence of an output schema.

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 the baseline is 3, but the description adds meaning the schema does not: the timezone fallback ('local Berlin time if no zone') for departure/arrival and the fact that from/to accept free-text names rather than requiring de: IDs. This meaningfully improves how an agent fills the parameters.

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 concrete verb+resource+scope: plan public-transport journeys from one stop to another in the Hannover GVH/ÜSTRA/DB network. This is clearly distinct from the sibling stop_search (stop lookup) and departures (departure board) without naming them, because the resource is a route between two stops.

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 explicit operating context: default is depart-now, and either departure or arrival can be set to plan for a specific time, with arrival/departure being mutually exclusive. It does not, however, say when to prefer this over stop_search or departures, so there is no alternative routing.

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