Plan a 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 explicitly describes what the tool returns (legs, times, transfers, disruptions) and clarifies the behavioral difference between soft preferences (prefer/avoid_lines) and hard exclusion (forbidden_uris). It stops short of describing edge cases or error behavior, but the core computational behavior is transparent.

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?

Three sentences, front-loaded with the primary function, and every sentence adds information: what it computes, what it returns, and how to express preferences/exclusions. No filler or repetition of schema details.

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 is complex (10 params, no output schema) and the description covers the main outcome and the most nuanced parameter behavior. It doesn't explain defaults like datetime=now, but the schema handles that. The return shape is sufficiently described for an agent to understand what it will receive.

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?

With 100% schema coverage, baseline is 3. The description adds value by explaining the exact semantics of prefer_lines/avoid_lines vs forbidden_uris, which the schema only hints at, and confirms that max_nb_journeys caps the result set. This goes beyond the schema's field-level descriptions.

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 opens with a specific verb ('Compute'), a precise resource ('public-transport journeys between two points'), and characterizes the routing as 'multi-modal door-to-door'. The return payload is spelled out (itineraries with legs, times, transfers, disruptions), which clearly separates this journey-planning tool from sibling schedule/stop endpoints.

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 implies the tool is for point-to-point journey planning but never states when to choose it over siblings like next_departures or stop_schedules. It gives no explicit when-not or alternative routing. The parameter guidance (prefer_lines vs forbidden_uris) is a usage guideline for the tool's own options, not for tool selection.

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