Vehicles

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

With no annotations, the description carries the full burden and does well: it names the upstream source (BusTime GTFS-Realtime), flags results as best effort, and declares historical occupancy out of scope. It does not state what happens when neither parameter is supplied, which matters for a tool with zero required parameters.

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 capability, then the exclusion, then the caveat. The field list is dense but every element (bearing, speed, crowding) is a concrete selection signal for the agent.

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?

An output schema exists, so return shape need not be explained, yet the description still summarizes the key fields and adds the data-quality caveat. The only missing piece is the semantics of calling with no arguments, which the zero-required-parameter schema leaves live.

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%, so the prose must supply meaning, and it does: `route` selects all vehicles on a route while `vehicle_id` is a fleet number for a single vehicle. It stops short of giving route format (number vs. name) or precedence when both are supplied, which is a real gap at 0% coverage.

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?

Opens with a specific verb+resource ("Live positions of the buses and streetcars") and enumerates the returned fields, so an agent knows exactly what it gets. It also carves itself off from the sibling `next_trains` by naming the rail lines it cannot serve.

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?

Gives an explicit when-not (rail lines 1, 2, 4, 5, 6 publish no positions), the resulting behavior ("answer unavailable"), and the concrete alternative (`next_trains`). This is the strongest possible form for a retrieval tool.

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