trimet_arrivals

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

Annotations already declare readOnlyHint=true, and the description is consistent with that, adding return value details (estimated/scheduled times, route info, vehicle status). No additional behavioral traits such as authentication, rate limits, or data freshness are disclosed, but the read-only context is adequately covered.

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, front-loaded with the primary action and scope, and includes relevant return details without extraneous text. No wasted words.

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 simple one-parameter read-only tool, the description covers the agency, location, mode, stop requirement, and returned data. It could optionally mention timezone or how to find stop IDs, but these are minor gaps for this category of tool.

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 fully documents the single parameter stop_id with an example ('8989' for Pioneer Square). The description adds no additional semantics beyond what the schema already provides, so 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 clearly states the tool retrieves real-time arrival predictions for TriMet buses and MAX light rail at a specific stop, with a specific verb ('Get') and resource. It distinguishes from sibling transit tools by explicitly naming TriMet and Portland, OR.

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 implies when to use the tool (when TriMet arrivals at a stop are needed) but provides no explicit comparisons or exclusions relative to sibling tools like cta_train_arrivals or marta_train_arrivals. The agency and stop-based scope give context, but no alternative guidance.

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