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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety burden is lifted. The description adds real context beyond them: results are limited to connections with *upcoming* trips and include the next departure, which tells the agent the result set is time-filtered. It does not mention ordering or result-size limits.

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?

One sentence of behavior followed by one sentence of usage, both front-loaded and free of padding. Every clause earns its place.

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 must speak to return content, and it does ('connections... with the next departure'). Combined with the usage framing, an agent has enough to call it correctly; minor gaps are ordering and any result caps, which would matter for a list endpoint.

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%, with enums fully documented for direction and language, so the schema carries the parameter burden. The description's 'from and/or to' phrasing loosely mirrors the direction parameter but adds no syntax or default information beyond it, making 3 the correct baseline.

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 ('List the connections... from and/or to a city') plus a scope qualifier ('currently have upcoming trips', 'with the next departure'). It implicitly separates itself from search_trips by framing itself as the pre-date-search discovery step, so an agent can route without opening a schema.

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?

Explicitly gives the use case ('Where can I go from Lviv?') and a sequencing rule ('before searching a specific date'), which is clear when-to-use guidance. It stops short of naming the alternative tool (search_trips) outright, so the routing is inferred rather than stated.

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