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

With no annotations provided, the description carries the behavioral burden and does so well: it discloses exactly what each mode reports, such as counts of on-time/delayed/cancelled departures and vehicle activity/delays. It does not mention output structure or behavior when both/no parameters are supplied, which is a minor gap.

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 concise sentences, with the core purpose front-loaded and each sentence devoted to one input mode. There is no redundant or filler wording.

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?

The description is adequate for common stop-or-line use, but because there is no output schema and no annotations, the lack of guidance on whether exactly one parameter is required and what happens when neither is supplied is a real gap. It also only sketches the response shape rather than naming specific fields.

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 already documents both parameters with 100% coverage, so the baseline is 3. The description adds value by explaining the semantic difference between the two parameters and what result each triggers, justifying a 4. However, the exclusivity of the two parameters is left implicit.

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 ('Get'), a clear resource ('realtime health summary'), and differentiates the two input modes with concrete outcomes. This distinguishes it from siblings like get_departures and get_vehicle_positions, which return raw data rather than aggregated health summaries.

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 gives clear usage context: pass stop_place_id for a stop-level summary and line_id for a line-level summary. It does not explicitly compare against sibling tools or state when not to use this tool, so it stops short of 5.

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