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

Annotations already cover safety (readOnlyHint, idempotentHint, openWorldHint, destructiveHint=false), so the bar is lower. The description still adds real value by disclosing the return payload (distance, time, steps, map link), the coordinate-format flexibility, and the openrouteservice/OpenStreetMap attribution, none of which annotations provide.

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 tightly written sentences front-load the core capability and then the input forms, with no filler. The trailing attribution is legally required boilerplate rather than waste, so size is appropriate, though it is not strictly agent-facing content.

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 by naming the returned fields (distance, travel time, turn-by-turn steps, map link). What an agent needs to call it correctly is present; only finer details like step/pagination limits are left to the schema.

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 all five parameters (from, to, via, mode, steps). The description reinforces the endpoint forms but adds no syntax or format detail beyond the schema, making the baseline 3 correct.

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 (get directions) and resource (routes between places), and names exactly what is produced: distance, travel time, turn-by-turn steps, and a map link. It is clearly distinguishable from siblings like get_location (single point) or find_places (discovery), so an agent can route to it without opening the schema.

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 description establishes clear usage context by defining the supported modes and the accepted endpoint forms (town, business/landmark, street address, lat,lon), which tells the agent when this tool fits. It does not, however, compare itself to siblings or state explicit exclusions, so it stops short of full when/when-not guidance.

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