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 new behavior beyond that: the result is a range in EUR, broken down per country, and may be flagged as partial when a country on the route lacks data.

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?

A single front-loaded sentence with the verb first and no filler; every clause carries information. It is dense rather than wasteful, though the stacked clauses make it slightly harder to scan than a two-sentence split would be.

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 correctly compensates by describing the return shape (EUR range, per-country breakdown, partial-result flag). Nothing essential for correct invocation is missing, though the undefined partial-result semantics could be spelled out further.

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 the 2-10 waypoint rule, ordering semantics and the vehicle_class enum, so the baseline is 3. The description only restates the element count and says nothing about locale or vehicle_class that the schema does not already cover.

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 ('Estimate toll cost for a road trip') plus the input shape (2-10 place names) and output form (EUR range with per-country breakdown). It is clear and precise, but it never names the obvious sibling get_toll_rates, so an agent must infer whether this is the lookup-table tool or the route estimator.

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 implied rather than stated: the description makes clear this is for multi-stop trips of 2-10 place names, which scopes the tool, but it offers no when-to-use/when-not and no comparison to alternatives such as get_toll_rates.

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