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

The readOnlyHint annotation covers the read-only behavior, and the description adds the useful caveat 'Only the TTC today', but it does not describe what the tool returns or how it behaves when no agencies exist.

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 very brief and contains no filler. It efficiently communicates the core scope, though it is a fragment rather than a full 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?

Given the minimal schema and no output schema, the description is too sparse to be fully self-contained. It omits parameter semantics and usage guidance, leaving an agent to infer how to call the tool and interpret results.

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 0% and the description provides no meaning for the 'limit' or 'fields' parameters. The parameter names hint at their purpose, but the description does not compensate for the lack of schema descriptions.

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 title indicates 'list agencies' and the description says 'The transit agencies covered', which is fairly clear but lacks an explicit verb and does not differentiate from sibling tools like transit-toronto_get_routes or transit-toronto_get_alerts.

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?

No guidance is provided about when to use this tool versus alternatives such as getting routes or alerts. The description only states scope, not usage context or prerequisites.

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