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

With no annotations, the description carries the full burden and does so well: it discloses that it never signs in, buys, creates an order, or guarantees checkout, and that the verdict is soft ('appears buyable'). It also surfaces a per-call cost of $0.003 USDC per successful call, which is meaningful operational context. It stops short of describing latency, rate limits, or auth needs, keeping it off 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?

Three short sentences, front-loaded with the core verdict and followed by the scope caveat and cost. No filler, though the cost sentence could arguably be metadata rather than description content.

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?

With no output schema and no annotations, the description must carry the load, and it does communicate what the result means (buyable vs explicit blockers like out-of-stock or unknown). It omits any detail about the nested variant object's expected shape or the result payload structure, which is a modest gap rather than a critical one.

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 the schema already documents all three parameters (url, variant, quantity). The description adds no syntax, format, or interpretation detail beyond the schema, so the baseline 3 applies; note the nested 'variant' object is left entirely to 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 precise verb+resource: reporting whether a public item 'appears buyable' and surfacing explicit blockers. It implicitly differentiates from the sibling commerce_availability by framing the result as a buyability verdict with blockers, but never names or contrasts the sibling, so an agent must infer the boundary.

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?

'This is a preflight only' tells the agent this is a pre-purchase check and explicitly not a purchase step, which is useful scoping. However, it gives no explicit when-to-use guidance relative to commerce_availability or domain_preflight, leaving the choice between sibling tools to inference.

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