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

Annotations already declare readOnly/openWorld/idempotent, so the safety profile is covered. The description adds behavioral value by asserting authority for geocoding and describing what each result contains (stop id, name, direction, serving routes), which helps an agent decide whether a second call is needed. It omits rate limits or error behavior, keeping 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?

Two sentences, zero filler: the first delivers the resource and payload, the second delivers the routing rule to trimet_arrivals. Nothing is buried or repeated.

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 carries the burden of describing results and does so (stop id, name, direction, routes), and the required API key is documented in the schema. Minor gaps remain around radius semantics and failure modes, but an agent has what it needs to call this correctly.

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 schema already documents latitude, longitude, meters (default 500) and _apiKey. The description only implies the coordinate pair and the Portland-metro constraint, adding no syntax or format detail beyond the schema — the baseline 3 is appropriate.

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+resource ('TriMet stops near a latitude/longitude') and enumerates the return fields (stop id, name, direction, routes), which lets an agent distinguish it from trimet_arrivals and trimet_vehicles without opening schemas.

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?

Explicitly names the downstream consumer and the condition that selects this tool: it is 'AUTHORITATIVE for turning a Portland address or coordinate into the stop ids trimet_arrivals needs.' This is a clear when-to-use plus a named alternative, not inference.

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