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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), and the description goes beyond them by disclosing the payload contents — cause, effect, affected routes/stops, and active period. It does not mention rate limits, result caps, or auth expectations beyond the _apiKey schema entry, which keeps it from 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?

Two sentences, zero filler, with the resource scope front-loaded and the authority claim last as a decision cue. Every clause carries information an agent would otherwise have to guess.

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 usefully enumerates the fields each alert carries, so an agent knows what it will get back. What is missing is the shape of the envelope — whether all alerts for the operator return at once, any result caps, or ordering.

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 100%, so the agency code and API key are already documented in the schema, and the description adds no format or syntax detail. The baseline 3 applies when the schema carries the parameter burden.

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?

Names a specific verb+resource (current service alerts) plus the operator scope and enumerates the alert types covered: delays, detours, elevator outages, planned closures. The explicit authority claim (“is there disruption on BART/Muni right now”) cleanly separates it from bay511_stop_predictions, bay511_vehicles, and bay511_operators.

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?

Gives clear context for when to reach for it — real-time disruption questions — and the schema/description pair points to bay511_operators for the required agency code. It stops short of naming an explicit alternative or when-not-to-use condition, so it is context-rich but not fully routed.

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