bus_departures

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint), so credit here goes to the added distinction that tracked buses carry an expected time and `delay_seconds` while untracked ones fall back to timetabled time with source `gtfs_scheduled`. That is genuine behavioral context beyond the structured fields, though no rate limits or auth requirements are mentioned.

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 sentences, front-loaded with the core question of what the tool returns, with no filler. The parenthetical is slightly dense but each clause carries distinct information.

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 an output schema present, return format need not be explained, and annotations carry the safety profile. What is missing is coverage of the undocumented input parameters, especially the required `atcocode`, which leaves the definition only minimally adequate for a 4-parameter tool.

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 0% for 4 parameters, so the description must compensate and largely does not. It explains the alternate values of `board`, but `atcocode` (the required identifier), `limit`, and `minutes_ahead` receive no explanation at all, leaving the agent to guess their format and units.

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 concrete resource and scope: 'What is leaving ... a bus stop', with the board='arrivals'/'both' variant spelled out. The word 'bus' implicitly separates it from the sibling rail_departures, though it never names or contrasts that sibling explicitly.

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?

It clarifies the board parameter's alternative modes (departures/arrivals/both), which is useful usage context, but gives no guidance on when to prefer this tool over siblings like live_buses or rail_departures. Usage is only implied by the tool name and resource.

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