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

Annotations already signal idempotency and non-read-only behavior, and the description adds essential operational traits beyond that: paid service credits per successful call, the need for prepared arguments, recovery via reused requestId, and that a new requestId is a new billable operation. This meaningfully extends the annotations and matches the idempotentHint.

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 well-ordered: core behavior first, then billing, prerequisites, and recovery semantics. Every sentence earns its place, and there is no wasted wording or repetition of schema details.

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 nested, paid, externally prepared tool, the description is quite complete: it covers purpose, prerequisites, authorization, billing, and idempotent recovery. The output schema exists, so return values need not be described here; the main gap is the lack of explicit nested-parameter guidance, but the schema and purpose largely cover that.

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 67% at the top level, and the description gives conceptual context for key inputs like required count, exact prices, and pack limits. However, it does not explain nested fields such as currency, minorUnitDigits, or the relationship between offers, unitsPerPack, and maxPacks beyond the schema's structural constraints.

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 specific verb and resource: 'Choose the lowest-cost whole-pack combination for a required count.' It clearly differentiates this tool from siblings like commerce_unit_price or commerce_price_components by emphasizing whole-pack combination optimization with explicit pack limits.

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 gives clear usage context: first call agent_utilities_prepare, requires existing credits and a private Authorization header, and warns about billing per requestId. It does not explicitly state when not to use this tool versus alternatives, but the prerequisites and cost model are actionable.

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