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

With no annotations and no output schema, the description carries the full behavioral burden, and it does so well for outputs: it enumerates every response field and exactly what each detail level adds, including geometry, lookup traces and formula variables. It omits operational behavior such as auth requirements, rate limits, or failure modes for unsupported routes, which keeps it from 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?

Purpose is front-loaded in one sentence, followed by a dense but justified field inventory that substitutes for the missing output schema. There is mild redundancy where the detail=detailed/full semantics restate the schema's own descriptions, but no filler sentences overall.

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 no output schema and a nested vehicle object, the description supplies the return-value structure that would otherwise be missing, covering all detail levels and nested segment fields. What remains absent (auth, error handling) is secondary for a read-style cost estimator.

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 the baseline is 3. The description goes beyond the schema by spelling out what 'detailed' and 'full' actually return (segments, geometry, source_url, matched_geofence, formula_vars, lookup_trace) and by noting that origin/destination gain lat/lon at full detail — information the terse schema descriptions do not convey.

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 opens with a precise verb+resource ('Calculate European road toll costs') and narrows scope to heavy trucks/commercial vehicles across 40+ countries. The only sibling, get_quota, is functionally unrelated, so no meaningful disambiguation is required. An agent can immediately tell what this tool produces.

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 tool clearly belongs to toll-cost estimation, but there is no explicit 'use this when…' clause, no exclusions (e.g. non-European routes, passenger vehicles), and no prerequisites or limits. The detail-level explanation partially guides parameter choice but not tool selection.

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