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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds useful operational context: the API is keylessщам, data is real-time only where the operator publishes it, and the exact departure fields returned are enumerated. This complements the annotations without contradicting them.

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 compact and front-loaded: it states the purpose in the first sentence, then gives the key input pattern, output summary, and access/caveat in the next two sentences. Every sentence earns its place with no redundancy.

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 read-only query tool with all parameters documented in the schema texting, the description covers the essential behavioral context: what it returns, how to specify the station, and real-time availability limits. It does not explicitly mention defaults like results=15, but the schema already covers that. The only real gap is explicit sibling routing.

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?

The input schema provides full descriptions for all four parameters, so the schema covers the heavy lifting. The description reinforces the id parameter's accepted forms but does not add significant new parameter-level meaning beyond what is already in the schema.

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 clearly defines the tool as a live departures board for German/European stationsasi, with a specific resource and output set of departure fields. It relies on the tool name and sibling context to distinguish from dbrail_arrivals and dbrail_journeys rather than explicitly naming them, so it misses the top score but is still clear.

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 description gives practical input guidance: pass a station name or a dbrail_locations stop id, and notes the keyless, real-time caveat. It does not explicitly explain when to choose this over dbrail_arrivals or dbrail_journeys, so usage is mostly implied rather than stated.

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