bart_departures

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

The readOnlyHint annotation already signals a safe read operation. The description adds value by disclosing the exact return fields (departure times, platform, direction, train length, color) and the special 'ALL' station option, going beyond what the annotation provides. No contradictions exist.

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 resource, and every clause adds useful information. No filler or redundancy.

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 single-parameter read-only tool with a 100%-covered schema, the description covers the return fields (since there is no output schema), the input format, and the special 'ALL' behavior. It is fully self-sufficient for an agent to select and invoke the tool correctly.

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 describes the 'station' parameter with examples at 100% coverage, so the baseline is 3. The description adds the general rule that abbreviations are 4 letters and explains the 'ALL' special value, enriching the schema's example-based documentation.

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 real-time departure estimates for a BART station,' which is a specific verb+resource with clear scope. It also confirms the return payload (departure times, platform, direction, train length, color), which distinguishes it from sibling tools like bart_advisories and other transit arrival tools.

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 clearly states what data this tool provides (real-time departures for a BART station) and gives station abbreviation conventions. It does not explicitly say when not to use it or name alternatives, but the context makes its purpose unambiguous among the many transit sibling tools.

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