stl_gtfs_coverage

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

Annotations already indicate read-only and idempotent. The description adds functional behavior (returns coverage range and days remaining) and the reason for expiration (quarterly feed), which is helpful context beyond the annotations.

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 concise and well-structured: first sentence states the core function, second sentence provides contextual advice. No unnecessary fluff.

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?

While the tool's purpose and usage context are clear, the description lacks any explanation of the 'snapshot' parameter. This is a significant gap that could lead to incorrect invocation, especially since the parameter is optional and its default behavior is unknown.

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 provides no description for the 'snapshot' parameter, and the tool description does not explain it at all. With 0% schema coverage, the agent receives no guidance on what this parameter represents or whether it is required.

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: to provide the service date range and days remaining before the feed expires. It is distinct from sibling tools like stl_gtfs_schema and stl_gtfs_stats.

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 explicitly advises when to use this tool: 'Check this before trusting any departure result.' It also explains the context (empty departures may be due to expired feed) and indirectly differentiates from stl_gtfs_departures and stl_support_explain_empty.

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