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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering safety and mutability. The description adds value beyond these by mentioning the MassDOT Open Data License and no upstream cost, as well as the behavioral aspect of returning route IDs used in downstream tools. It does not repeat annotation info or contradict it.

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: the core purpose is front-loaded, then return fields, downstream usage, filter codes, and licensing follow in logical order. Every sentence adds useful information with no fluff or redundancy, making it efficient and easy to scan.

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 an output schema available (as signaled) and thorough parameter schemas, the description covers all essential aspects: what it does, what it returns, how the output is used, the filter options, and licensing/cost. No critical information is missing for an agent to call this 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?

Schema description coverage is 100%, with each parameter (sort, type, limit) documented in the schema. The description repeats the type codes but adds no new meaning beyond what the schema provides. It does offer context on route IDs used elsewhere, but that is not parameter-specific, so the added semantic value is minimal, aligning with the baseline of 3.

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 lists Boston MBTA transit routes by type, with a specific verb and resource. It distinguishes from siblings by explicitly focusing on routes and mentioning that returned route IDs are used by related tools, making it unambiguous which tool to select for route listing.

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 implicitly indicates usage: it lists routes, and further states that route IDs are used as filter inputs for mbta-transit.stops, alerts, and predictions, guiding the agent on how this tool fits into a workflow. It does not explicitly state when not to use it, but the distinct purpose and sibling names make alternatives clear, so it provides adequate usage context.

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