stl_gtfs_service_day

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

The description states that it returns service date(s) and corresponding gtfs_time values, which is helpful. Annotations already indicate read-only, idempotent behavior, so the description adds meaningful behavioral detail without needing to restate side effects.

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 brief and to the point, with no redundant wording. Every sentence adds value: the purpose, the usage condition, the GTFS convention, and the parameter definition.

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 this is a simple single-parameter tool with read-only annotations and a clear domain explanation, the description is complete enough for an agent to decide when to use it and what to expect. The DST note addresses the key subtlety relevant to this 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 schema only specifies timestamp as an optional string/null, but the description adds crucial semantics: ISO-8601 instant format, naive values interpreted as America/Chicago, and the timezone-related DST explanation. This fully compensates for the 0% schema coverage.

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's purpose: determining which GTFS service date(s) a wall-clock instant could belong to and providing the corresponding gtfs_time. This is specific and distinct from sibling tools focused on routes, stops, departures, or other GTFS aspects.

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?

It explicitly says 'Use this whenever a departure time looks off by a day,' giving a concrete condition for when to invoke the tool. It also explains the GTFS time convention and DST nuance, providing important context for correct use.

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