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 real behavioral context beyond that: results are grouped by agency, include walk time and GTFS service windows, and gain a feasibility check when day/time are supplied. It also flags that the tool is unofficial and unaffiliated with WMATA, which is meaningful provenance information an agent cannot get from 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?

Two compact body sentences front-load the core behavior before the parameter note, with no filler. The closing grounding and disclaimer sentences are longer than strictly necessary but serve a real anti-hallucination and provenance purpose.

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 no output schema, the description correctly describes the return shape: routes grouped by agency, each with walk time and service window, plus per-connection feasibility. Combined with annotations and the unofficial disclaimer, an agent has nearly everything needed; the only gap is how `place` should be formatted.

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 0%, so the description carries the full burden, and it does most of the work: `day` is illustrated with 'saturday' and `time` with 'HH:MM', and their combined effect (per-connection feasibility check) is stated. `place` is only implied via 'a station or stop' in the opening sentence — no guidance on whether it takes a name, ID, or coordinates — which keeps this below a 5.

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 gives a specific verb-and-resource: routes from OTHER systems reachable on foot from a station/stop, grouped by agency with walk time and service window. The emphasis on 'OTHER systems' and 'reachable on foot' distinguishes it from single-agency route lookups like get_route or get_metro_route. It stops short of naming a sibling tool outright, so a 4 rather than a 5.

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?

It explains how to use the optional parameters ('Pass `day` and/or `time` to get a per-connection feasibility check'), which implies the base use case versus the enriched one. However, it never states when to choose this over plan_connection or plan_trip, nor any exclusions or prerequisites. Usage is inferable but not spelled out.

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