wmata_train_positions

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

The annotation readOnlyHint=true already indicates a safe read operation. The description adds that the tool returns real-time positions for all WMATA trains system-wide, which is useful scope context. However, it does not describe the response structure (e.g., coordinates, train IDs, line designations) or any refresh/update behavior. With annotations present, this is acceptable but not particularly rich.

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 a single sentence that conveys the essential purpose without any fluff or repetition. It is well-structured and front-loaded with the action verb.

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?

This is a simple zero-parameter tool, and the description clearly states its scope (all WMATA trains, real-time positions). However, there is no output schema and the description does not explain what 'positions' means concretely (e.g., lat/long, station-to-station progress) or what fields will be returned. This is a moderate gap for an agent that might need to interpret the data.

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 tool has zero parameters, so the input schema fully covers parameter semantics. The baseline score of 4 is appropriate because there is nothing to document beyond the schema.

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 uses a clear active verb ('Get') with a specific resource ('real-time positions of all WMATA Metro trains on the system'). This distinguishes it from sibling tools like wmata_train_predictions (predictions) and wmata_bus_predictions (buses), as well as other transit systems (SEPTA, BART, etc.).

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?

No guidance is provided about when to use this tool versus alternatives. For example, it does not mention wmata_train_predictions for train arrival predictions, nor does it clarify whether this tool is for geographic positions vs. arrival times. There are no exclusions or alternative tool recommendations.

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