Search A to B public transport connections

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

Annotations already provide readOnlyHint, openWorldHint, idempotentHint, and no destructiveness. The description adds value by listing return details (legs, transfers, times, realtime status, tracks, accessibility) and stating limitations (no ticket sales, accuracy not guaranteed). However, it does not explicitly mention that the tool queries an external service or that rate limits may apply, though the usage warning implies responsible usage.

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?

Description is concise, front-loaded with the primary purpose, and every sentence adds value. It efficiently covers purpose, return values, limitations, and usage policy without unnecessary verbosity.

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?

Given the tool's complexity (10 parameters, no output schema), the description covers purpose, return values, limitations, and usage policy. While it does not detail the exact output structure, mentioning 'legs, transfers, times, available realtime status, tracks, and accessibility fields' provides sufficient context. The lack of an explicit output schema is compensated by the description, but some agents might benefit from more structured return info.

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 each parameter already has a description. The tool description does not add additional parameter semantics beyond what is in the schema. Per guidelines, baseline is 3, and no extra information is provided.

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?

Description explicitly states 'Plan public transport journeys between two station names using Transitous/MOTIS.' The verb 'plan' and resource 'journeys' are specific, and the tool clearly distinguishes from siblings like execute_api_action or search_locations which handle generic actions or location lookups.

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?

Description provides clear guidance: 'It does not sell tickets or guarantee accuracy.' It also includes a detailed usage warning about Transitous being volunteer-run, best-effort, and intended for FOSS/non-profit use, with specific instructions on User-Agent, caching, traffic limits, and contacting before intensive use. This effectively tells the agent when and how to use the tool.

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