Get arrival times at a stop

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

The annotations already declare readOnlyHint and openWorldHint; the description helps confirm these by saying 'Estimated'. It adds no operational limitations beyond what the schema provides, and it doesn't mention any rate limits, pagination, or fallback/ambiguous name handling. It does add 'service alerts' as a kind of output, which is lightly useful, so the description is adequate but not deep.

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 capture the main purpose, input flexibility, and key fields. The most important information is placed first. No filler is present.

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?

For a read-only tool with four parameters fully documented in the schema and an output schema present, the description provides enough context for an agent to know what the tool is for, what it accepts, and what it returns. It does not need to restate schemas because those are adjacent.

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 schema has 100% coverage of four parameters, each with its own description. The text like 'stop id, stop code, or part of a stop name' mainly restates the schema's stop description. It adds no extra meaning for limit, mode, or route, so meaning comes primarily from the schema itself.

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 names the resource ('estimated arrival times of buses or trains') and the specific action ('at a specific stop or station'), making the tool's function explicit. It also lists the input formats and useful output fields, which differentiates it from sibling tools find_vehicle and list_vehicles.

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 implies when to use the tool (when you need arrival times at a stop), but it never states an explicit 'when-not-to-use' or contrasts with siblings. No exclusions are given, so an agent can infer intent, but someone selecting among the three siblings must rely on whatever context the user provides without extra guidance.

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