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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=false), and the description adds genuinely useful non-schema context: this is a paid x402/USDC call at a flat $0.1, and unknown ids incur no charge. Coverage breadth ('ANYWHERE in the 103,372-variant catalogue') is also disclosed. It does not mention rate limits or cost scaling beyond the flat fee.

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 tightly packed sentences: capability and scope first, cost model second. Every clause carries information (breadth, count range, language count, price, refund-on-unknown-id) and nothing is redundant.

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-value explanation is unnecessary. Between the description (scope, batch size, languages, cost) and the schema (id format, bounds, locale enum), an agent has everything needed to decide and invoke correctly.

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%, so both parameters (variant_ids and the 20-value locale enum) are already fully documented, including the 2-4 bounds and the description of locale behavior. The description only echoes the 2-4 range and '20 languages', adding no syntax or semantic detail beyond the schema.

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 — side-by-side localized specs for 2-4 variants — plus scope (anywhere in the 103,372-variant catalogue) and language coverage. However it never names or contrasts with the sibling compare_variants, so an agent must infer the difference from the 'full'/'anywhere' framing alone.

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 pricing clause ('paid per call... not charged when an id is unknown') implicitly frames when this is worth calling, and the 2-4 variant limit signals batch use. But there is no explicit when-to-use versus compare_variants or when-not-to-use guidance, leaving the sibling choice to inference.

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