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

Annotations already declare readOnlyHint, destructiveHint=false, openWorldHint and idempotentHint=false, so the safety profile is covered. The description adds genuinely useful data traits beyond that: bus feed long names are empty and trip headsigns must be used for destinations, and the per-system route counts set expectations for result volume. It stops short of stating whether system filters reduce the result or how results are ordered.

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?

Four short, front-loaded sentences, each carrying concrete information (counts, the bus short_name caveat, PATH scope) with no filler. Line-broken formatting is slightly awkward but does not impede scanning.

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?

An output schema exists and annotations cover safety, so return-value detail is rightly omitted. The remaining gap is the system parameter's accepted values and the relationship between the enumerated systems and that filter, which the description only hints at.

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?

There is one parameter ('system') with 0% schema description coverage and only a default of 'all'. The description partially compensates by naming the three systems (NJ Transit, NJ bus, PATH), which implies the accepted filter values, but it never states that these are the values for the system parameter or what an invalid value does.

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 supplies the verb ('List all routes') and the description states the resource precisely: all lines/routes across NJ Transit rail/light-rail, NJ bus, and PATH, with route counts. Sibling tools (next_departures, trip_between, etc.) are clearly different operations, so no sibling differentiation is needed. The description text itself never states the verb, relying on the title.

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?

There is no when-to-use guidance, no mention of prerequisites, and no routing to alternatives such as search_stations when the caller only needs one route. The enumeration is implicitly the lookup step for route IDs, but that is left to inference.

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