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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds only the empty-query behavior and the available kinds; it says nothing about result ordering, pagination past the limit, or what happens with an unrecognized query.

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?

Three short sentences, front-loaded with the core action and the fallback behavior. The 'Kinds:' enumeration largely repeats the schema's kind description, which is the only mild redundancy.

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?

For a simple four-param search tool with an output schema and full annotation coverage, the description supplies what's needed to call it correctly. The main omission is routing guidance relative to sibling transit tools, which is a minor gap.

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 coverage is 100%, so all four parameters are already documented in structured form. The description reinforces the query semantics ('by number or by name', empty = all) but adds no format detail such as case sensitivity or partial-match rules beyond what the schema states.

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?

States a specific verb and resource ('Finds the routes of the TTC') plus the two lookup modes (by number or by name), which distinguishes it from transit_get_route in practice. It doesn't explicitly name that sibling, so the differentiation is implied rather than stated.

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 clause 'With no query, lists every route' gives one useful usage condition — the browse-all case. There is no guidance on when to use this versus transit_get_route (fetch one route's detail) or transit_search_stops, so the agent must infer the boundary from tool names.

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