Detours

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

With no annotations, the description carries the burden and adds real signal: it discloses the upstream data source (TTC's own site endpoints), the 'best effort' reliability caveat, the grouping key, and null semantics for the reason field. It omits freshness/refresh expectations and whether results are cached, which keeps it short of a 5.

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?

Resource and scope are front-loaded in the first clause, and the second sentence delivers the data-quality caveat without padding. The middle enumeration is dense but every item maps to real returned content.

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?

The output schema exists, so return values need no prose explanation, and the data-source caveat is covered. However, for a tool with no annotations and a completely undocumented sole parameter, the description should say how 'route' filters results and when to prefer alerts/service_changes.

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% for the single 'route' parameter, and the description never mentions it — no explanation of accepted route identifier format, whether it narrows to one route, or what omitting it returns. That leaves the only input entirely undocumented across both prose and schema.

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 names a specific resource (active surface detours from the TTC TripModifications feed) and enumerates the per-detour payload, so the agent knows exactly what comes back. It does not explicitly distinguish itself from siblings like alerts or service_changes, though the 'service change' mention gives a partial hint at the boundary.

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 statement of when to call this instead of alerts or service_changes, nor any prerequisites or exclusions. The phrase 'Active surface detours' implies the use case, but an agent comparing three similarly-themed siblings gets no routing guidance.

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