wmata_train_predictions

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

Annotations already declare readOnlyHint=true, so the safe-read nature is covered. The description adds modest context by clarifying that omitting the station parameter returns predictions for all stations, but it does not disclose data freshness, prediction horizon, or rate limits. This is acceptable with the annotation coverage.

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 redundant content. The first sentence states the core function, and the second provides essential station code examples and default behavior.

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?

Given the tool has a single optional parameter and no output schema, the description covers the main usage scenarios: requesting predictions for a specific station or all stations. It could optionally describe the structure of the returned predictions, but the basic purpose and station specification are clear.

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 already documents the 'station' property with 'Station code (e.g., 'A01') or 'All' for all stations' (100% coverage). The description adds value by providing concrete station code mappings ('A01=Metro Center, B01=Gallery Place') and explicitly stating that omitting the parameter is equivalent to 'All'. This goes beyond the schema's brief example.

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 opens with 'Get next train arrival predictions at a WMATA Metro station' – a specific verb and resource. This clearly distinguishes it from sibling tools like wmata_train_positions and wmata_bus_predictions.

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 on when to use this tool versus alternatives is provided. The description only gives station code usage instructions ('Use 'All' or omit for all stations'), but does not mention related tools like wmata_train_positions or transit_arrivals. The agent must infer selection from the tool name and sibling context.

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