Next scheduled buses from a stop

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

Since no annotations are provided, the description carries the full burden. It explicitly notes that the data are timetable times and that CityBus does not provide a public real-time feed, so buses may run early or late. This is a critical behavioral disclosure that goes beyond the schema.

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 two sentences long and immediately states the purpose and key constraint. Every sentence adds value with no wasted words. It is front-loaded and highly scannable.

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 is relatively simple (3 fields, no output schema, no nested objects), the description covers the essential behavior (timetable only, source). It does not describe the return format, but that is acceptable since no output schema exists and the data is straightforward. A small gap is that it doesn't explain how the limit parameter affects output beyond 'default 10' from the schema.

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?

The input schema already provides descriptions for all three parameters (100% coverage). The tool description adds no further elaboration on the parameters. The baseline for full schema coverage is 3, and the description meets that without adding extra parameter insight.

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 clearly states the tool provides 'Next scheduled CityBus departures from a stop today, by route and headsign.' It specifies that these are timetable-based times and not real-time, which is a key distinction. The source is also mentioned. This clearly differentiates from sibling tools like bus_stops or bus_routes.

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 implicitly tells the agent when to use this tool (to get departure times) and highlights a limitation (no real-time data). It does not explicitly discuss when not to use it or mention alternatives among siblings, but the constraint is clear enough for an agent to decide.

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