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

Annotations already establish the read-only, idempotent, non-destructive profile. The description adds meaningful behavior beyond that: per-day rate selection, listing no-rate trips with reasons instead of dropping them, and the 'Never metered' operational note. This exceeds the lower bar set by the annotations, though 'Never metered' is slightly ambiguous.

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 description is compact and front-loaded with the core summary output, then adds edge-case behavior and defaults. Every sentence earns its place, but 'Never metered' is cryptic and could be clearer or removed.

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?

Given there is no output schema, the description does a good job enumerating output contents, grouping, rate behavior, and no-rate handling. It is slightly incomplete regarding the exact structure of the response and leaves 'distance kept per unit' unclear, but overall it is sufficient for correct invocation.

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?

The schema already provides 100% parameter documentation, including defaults and the category enum values. The description reinforces date-range and category concepts but does not add significant semantic detail beyond the schema, so the baseline score of 3 is appropriate.

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 clearly identifies a mileage summary over a date range, including trips, per-day rates, deductible amounts, and per-currency totals. It is specific enough to distinguish from most siblings, though it never explicitly differentiates itself from mileage_export or trip_list.

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 implies usage for aggregate deductible-mileage reporting and states the current-calendar-year default. However, it gives no explicit guidance about when to choose this tool over mileage_export or trip_list, leaving the routing to inference.

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