List all vehicle positions

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is established. The description adds the behavioral fact that it returns 'current' coordinates and only vehicles 'in service,' which clarifies the data scope. It does not go beyond that (e.g., mention of latency, rate limits, or pagination), so it makes a modest addition beyond the annotations.

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 with no waste. The core action is front-loaded ('Return the current GPS coordinates...'), and the optional filters are mentioned compactly. Everything written earns its place, making it highly efficient for an agent to parse.

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 is present, so return format details are not needed in the description. The tool is a simple listing operation with optional filters; the description covers the essence, and the schema covers parameters. The only minor gap is the lack of explicit mention of potential limits (like pagination), but the limit parameter and output schema mitigate this. Overall, it is sufficiently complete for an agent to invoke correctly.

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 67%, meaning most parameters already have meaning in the schema (mode, limit, and route each have descriptions). The description repeats these filters ('buses or trains', 'single route') without adding extra semantics like value formats or edge cases. Since the schema already covers the parameters, the baseline of 3 is appropriate.

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 specific verb ('Return'), a clear resource ('GPS coordinates of every CATS bus and train in service'), and explicitly distinguishes this from a single-vehicle lookup ('every'). It also mentions optional filters, which makes the tool's scope unmistakable and separates it from the sibling find_vehicle.

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 says 'Optionally filter to buses or trains, or to a single route,' which gives clear context on how to narrow results. However, it does not explicitly state when to prefer this tool over siblings like find_vehicle (e.g., 'for all vehicles, use this; for a specific one, use find_vehicle'). The 'every' phrasing implies bulk listing but does not name alternatives or exclusions.

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