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 genuinely useful behavior: results are computed against live traffic, traffic delay is reported separately from free-flow time, and four travel modes are supported. It does not discuss rate limits or API-key/quota behavior, but that is documented in the schema.

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?

Front-loaded with the core purpose, then the differentiators (traffic delay, ETAs, travel modes), then an example. Every sentence carries information, though the inline example largely duplicates the two examples already present in the input schema, which is minor redundancy.

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?

For a simple read-only routing tool with no output schema, the description does the necessary work of stating what comes back (distance, travel time, traffic delay) and what modes are accepted. Only the response's precise shape and units (metric vs imperial) are left implicit, which is a small gap.

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%, including origin/destination lat-lon labels and the travel_mode enum with its default, so the schema carries parameter meaning. The description repeats the mode list and shows an example call but adds no coordinate-format or unit conventions beyond what the schema already states. Baseline 3 applies.

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: 'calculate the best route between two points and return distance plus travel time computed with live traffic.' It also names the output payload (distance, travel time, traffic delay), which cleanly separates it from siblings like geocode, reverse_geocode, and search_poi.

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?

The phrase 'Traffic-aware routing / directions' plus the travel_mode list gives clear context for when this is the right call (point-to-point ETA rather than address lookup). It stops short of explicitly naming alternatives such as geocode or search_within, so there is no stated when-not-to-use rule.

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