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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered elsewhere. The description adds the useful fact that this is a descriptive lookup returning terms and review scores, but says nothing about data currency, coverage gaps, or whether missing suppliers are omitted versus nulled.

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 sentences, both load-bearing: the first defines the payload, the second defines the trigger, and the trigger is placed last so the reader knows what the tool is before when to use it. The field enumeration is long but each item is genuinely part of the return shape.

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?

An output schema exists, so return values need not be re-explained, and the description therefore has spare capacity to focus on selection. With only two well-described parameters and full annotation coverage, an agent has nearly everything needed; the only real gap is not knowing how this differs from airport_costs and compare_airports.

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% and both parameters are documented in-schema with examples, so the baseline is 3. The phrase 'per supplier at an airport' and 'asks about a named supplier' hints that omitting the optional supplier parameter yields all suppliers at that airport, but the description never states that behavior explicitly.

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 enumerates exactly what is returned per supplier at an airport (daily price, second-driver fee, full-cover price, deposit, debit-card acceptance, review scores), which is far more specific than the title alone. It scopes to 'at an airport' but never names the adjacent siblings (airport_costs, compare_airports) it is not, so differentiation is left partly to inference.

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?

It gives a clear trigger: 'when the person is choosing between suppliers at one airport or asks about a named supplier.' That implicitly separates the single-airport comparison case from cross-airport ones, but no alternative tool is named and no exclusion is stated for when airport_costs or compare_airports would be the right call.

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