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

Annotations already declare this as a safe read (readOnlyHint=true, destructiveHint=false), and the description adds meaningful context beyond that: the subscription-key auth requirement, the returned payload fields (GeoJSON, distance, duration, maneuvers), and the side effect of elevation=true producing gain/loss. Rate limits and error behavior are not covered.

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?

Four short sentences, front-loaded with the core action and waypoint bounds, then options and the auth caveat. Efficient, though the enumerated costing list partially duplicates the schema enum.

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 return-value burden and does so (GeoJSON, distance, duration, maneuvers, elevation profile). The auth requirement is disclosed. Only minor gaps remain, such as behavior on invalid/duplicate waypoints.

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 costing, elevation, and the ordered 2–10 waypoint array. The description largely restates these (mode list, elevation gain/loss, waypoint count) without adding syntax or format details, so the 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?

The description gives a specific verb and resource ('Calculate a turn-by-turn route between 2–10 waypoints'), so an agent knows exactly what it produces. It does not name or distinguish itself from siblings like isochrone or geo_navigate, which also deal with routing/reachability, leaving some ambiguity in a crowded namespace.

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 when-to-use / when-not-to-use guidance and no alternatives are named. The agent is told what modes are supported and that a subscription key is required, but it must infer the conditions under which this tool beats isochrone or geo_navigate.

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