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

Annotations cover only the safety profile, and the description adds genuinely useful behavior the agent cannot get elsewhere: the data comes from the public OSRM router with no API key, it reflects free-flow road-network speed with no live traffic, and place names are resolved via Open-Meteo's geocoder. The free-flow/no-traffic caveat is exactly the kind of limitation that changes how a result should be presented.

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?

The core answer (duration + distance, routing source) is front-loaded in the first clause. The trailing sentence about Verse's rides family is tangential context that an agent doesn't need to call the tool correctly, slightly diluting an otherwise tight description.

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 returns, and it does state the two values returned (time and distance) plus the routing source. It omits units and what happens when a place name fails to geocode, which are the remaining gaps.

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 coverage is 100%, so both params are already documented, making 3 the baseline. The description goes further by naming the geocoding service used for name inputs (Open-Meteo) and confirming the 'lat,lon' string format, which adds provenance the schema does not supply.

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 resource and both outputs: how long the drive is and how far, between two places. The verb+resource+return shape is unambiguous, and no sibling tool overlaps with routing, so an agent can select 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?

Usage is only implied — the agent must infer 'use this when you need driving time/distance between two points.' There is no explicit when-to-use, when-not, or named alternative, though the note that 'Verse's rides family checks this same router' hints at related routing tooling.

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