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

Beyond readOnlyHint and openWorldHint, the description discloses a non-obvious failure mode: supplying fields triggers privacy_consent_required until the controller accepts the current privacy version, and the agent must not fabricate that acceptance. That is genuine behavioral context an agent could not infer, though the return payload shape is not characterized.

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 what the tool does, followed by exclusions and the consent caveat. No wasted wording, though the three separate 'does not' clauses could be tightened.

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 two-parameter read-only lookup the description covers the main risk (the privacy-consent gate), but with no output schema it never indicates what a connection result contains, and it leaves station-name formatting entirely to inference.

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 0%, so the schema documents only types and length limits for 'from' and 'to'. The phrase 'two station names' does tell the agent the intended value domain, but nothing is said about format, ambiguous names, or whether identifiers are accepted.

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 states a concrete verb and resource: fetch one connection between two station names from the Swiss public-transport API. That is enough to distinguish it from generic data hubs, though it never contrasts itself with the closest sibling, hub_rail-board.

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 exclusions ('does not sell a ticket', 'does not spend points', 'does not accept a URL') clearly fence off misuse cases. What is missing is positive routing such as when to prefer hub_rail-board or hub_geocode instead.

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