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

The annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false); the description adds the useful fact that the result is a metadata snapshot about the server's own data state, not a transit answer. It also enumerates the content dimensions (range, counts, live flag, feed age), though it does not mention whether the snapshot can be stale itself.

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 sentences, with the content inventory first and the decision rule second. The quoted question makes the intended use concrete without padding.

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?

With zero parameters, an output schema, and annotations that declare it a read-only, open-world call, the description gives everything an agent needs to decide when to call this tool instead of a departure or alert query.

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 takes no parameters, so the baseline is 4; there is nothing for the description to clarify and no mismatch to flag. It does not waste words restating a nonexistent input.

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 names the concrete contents the tool reports: 'GTFS date range and counts, whether live NJ data is enabled, PATH feed age.' That is far more specific than a tautology, and the 'live or scheduled' framing tells it apart from the query siblings passing through the same domain.

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?

'Use this to answer "is this live or scheduled?" honestly' gives a clear routing condition: call it when you need to validate data provenance before trusting a departure answer. No explicit when-not or sibling alternatives are named, which keeps it short of a 5.

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