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

Annotations declare readOnlyHint and openWorldHint, so safety is covered externally, and the description adds genuinely useful behavior: the return payload (times, platforms, operators, changes) and the time-sensitivity caveat that live delays only apply 'today'. It also discloses the Poland-only coverage boundary, which is not in any structured field.

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?

Two dense sentences with no filler; the core capability leads and the return/time-sensitivity details follow. Every clause carries information an agent needs to select and call the tool.

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 10-parameter, no-output-schema tool with only two annotations, the description adequately covers scope, accepted inputs and the shape of the result. It does not address no-connection or error outcomes, and transfer/arrive_by semantics are left entirely to the schema, but nothing essential to correct invocation is missing.

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%, so the schema already documents every parameter including formats, defaults and enum values for 'modes'. The description largely restates the from/to input forms ('station name', 'town', coordinates) already present in the schema properties, with only the 'Zakopane = all its stops' clarification adding marginal meaning.

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+resource ('Find connections between two places in Poland') and immediately scopes it to multi-modal routing including train/bus changes, which clearly separates it from siblings like departures and trip_details. The geographic scope (Poland) and the accepted origin/destination forms are stated up front.

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?

Usage is implied rather than declared: the description positions this as a point-to-point planner, so an agent can infer it is the right tool for route planning versus departures/trip_details. However, no sibling is named and no when-not-to-use condition is given, so routing is left to inference.

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