Compare travel times

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

Annotations already carry the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint), so the bar is low. The description adds genuine context beyond them: the operation is deliberately batched into one request to replace N direction calls, and results come back pre-ranked ('sorted fastest first').

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?

Three tight sentences with the ranking capability and batching scope front-loaded, followed by use cases and the sorting guarantee. No filler and no restatement of the title.

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 an output schema present, return values need no explanation, and the 100%-documented schema covers the inputs. The description supplies the batching rationale and routing alternative, leaving only minor gaps such as traffic-awareness via departure_time or transit-specific caveats.

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 mode, units, region, language, departure_time content/format, and the address/place-name/PLACE_ID input form. The description adds no parameter-level detail (e.g. which inputs accept place IDs), so 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 and resource: 'Rank destinations by travel time and distance from one or more origins in a single request.' The batching scope ('one or more origins', 'single request') plus ranking output clearly separates it from the single-pair siblings like goplaces_directions.

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 two concrete triggering scenarios ('which of these is closest to home', 'how long to each of these three offices') and names the alternative behavior it replaces ('one directions call per candidate'). It stops short of an explicit when-not-to-use rule, e.g. falling back to a plain directions call for a single origin/destination pair.

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