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

readOnlyHint=true already covers the safety profile, so the description is free to add value — and it does, disclosing that results come from real reports and are only returned when a sufficient number of reports exist (a gating/empty-result behavior not visible in the schema). It stops short of describing aggregation, freshness, or how sparse data is surfaced, so it's short of a 5.

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 tight sentences, purpose front-loaded and the availability caveat placed second where it belongs. No filler, though the phrasing is conversational rather than maximally information-dense.

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 read-only, 3-parameter tool with no output schema, the description conveys what data is returned (amounts paid, durations) but not the structure of the result or how the optional 'from'/'mode' narrow it. Adequate but leaves an agent guessing at the response shape and parameter effects.

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 33% — only 'from' is documented; 'to' and 'mode' rely on bare enums. The description adds nothing about route direction ('to' required, 'from' optional), what each parameter means, or how mode affects results, so it fails to compensate for the coverage gap.

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 (empirical cost and transit-time outcomes for a route) and verb is clearly retrievable, with 'actually paid'/'actually took' distinguishing it from quote-style siblings. It never names border_quote or door_cost_estimate explicitly, so the contrast is implied rather than stated.

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 'actually paid ... actually took ... from real reports' phrasing implies this is for historical/observed data rather than forward-looking estimates, which weakly routes against border_quote and door_cost_estimate. There is no explicit when-to-use, when-not-to-use, or named alternative, and the sample-size note is a caveat rather than usage guidance.

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