stl_gtfs_calendar

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

The description goes beyond the annotations by explaining the behavioral nuance of separating weekly patterns from exceptions, which is not covered by the readOnly/idempotent flags. It clearly indicates what the tool does without hiding side effects (there are none).

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 relatively concise and well-structured: it starts with the core functionality, then adds the distinguishing detail, and ends with parameter info. It avoids redundancy and is easy to parse, though slightly verbose in the second sentence.

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?

The description covers the main query purpose and one parameter but lacks an explanation of the output structure (despite the output schema) and the meaning of 'snapshot'. Given the existence of many sibling tools, the description is adequate for basic usage but not fully self-contained for complex scenarios.

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?

Only the 'on' parameter is explained in the description (ISO date, defaults to today), while 'snapshot' is entirely undefined. With two optional parameters and zero schema descriptions, the agent cannot fully understand how to use 'snapshot' or interact with snapshot-related siblings, leaving significant ambiguity.

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 conveys that the tool returns service_ids active on a given date, and it explains the distinguishing feature of showing weekly patterns and exceptions separately. It is specific enough to understand the tool's purpose, though it could more explicitly state that it returns query results.

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 does not name any alternative tools or provide guidance on when to use this tool instead of siblings like stl_gtfs_service_day or stl_gtfs_query. The contrast with 'pre-merged' is implicit but not tied to specific alternatives, leaving the agent without explicit selection criteria.

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