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

Goes well beyond readOnlyHint/openWorldHint by disclosing that v1 is called directly, redirects are not followed, no points are consumed, and that a privacy_consent_required state is returned until the controller accepts the current privacy version. It does not describe the shape of a departure record or any rate/error behaviour beyond the privacy gate.

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?

Four short sentences, front-loaded with the core capability, and every clause carries information (version choice, cost model, consent failure mode). The negative framing of "does not accept a URL" is slightly indirect compared to stating the accepted input form.

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 one-parameter read tool with annotations and no output schema, the definition covers the behavioural contract and the notable consent failure mode. The remaining gap is that without an output schema, the structure of a returned departure is never sketched.

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 0% and the single `station` string carries no description, so the description must compensate. "One Belgian station" adds a real geographic constraint and "does not accept a URL" narrows the expected value form, but it never clarifies whether a name, code, or ID is wanted or how to disambiguate similarly named stations.

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 verb and resource ("Read up to five departures from one Belgian station") plus the backing source (iRail v1 liveboard). The geographic and count scope distinguishes it from generic transit siblings like hub_transit and hub_ferry without needing to name them.

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 exclusions ("does not accept a URL", "does not spend points") which implicitly steer usage, but never says when to pick this over hub_transit or other station-data siblings, nor what input form is actually expected. Usage is inferable rather than stated.

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