Plan a Helsinki transit journey

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

No annotations are provided, so the description carries the full burden. It discloses internal geocoding, return structure (up to 5 itineraries with legs, modes, line numbers, real-time status), default departure time of 'now,' and the requirement for ISO 8601 timestamps with offset. This is strong behavioral disclosure for a read-only planner, though it does not mention error handling or reversibility.

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 three sentences: first states the purpose, second covers inputs and outputs, third addresses departure time. It is front-loaded with the main action and contains no filler or redundant wording.

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?

The tool has moderate complexity (5 parameters, no output schema). The description sufficiently explains input types, geocoding behavior, return format (itineraries with legs, modes, line numbers, real-time status), and time defaults. Given the absence of an output schema, this is a complete and self-contained description.

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 baseline is 3. The description adds some context—internal geocoding, default departure time, and output details—but these are largely redundant with the schema's per-property descriptions. It does not significantly enhance parameter understanding beyond what the schema already provides.

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 specific verb and resource: 'Plan a public-transport journey between two places in Greater Helsinki.' It clearly distinguishes the tool from siblings by focusing on journey planning, while mentioning internal geocoding for endpoints. This is a clear, non-tautological purpose.

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 provides clear context: use for public-transport journeys in Greater Helsinki, accepts place names/addresses, returns itineraries. It does not explicitly mention when not to use it or alternatives like geocode or stop_departures, but the purpose is well-scoped enough to avoid confusion with the siblings.

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