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

Annotations already establish that this is a non-read-only, open-world operation, and the description does not add behavioral details such as payment mechanics, side effects, or reversibility. The brief phrase 'Buy...' restates the mutation already indicated by annotations, so beyond annotations it contributes little.

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 one short, front-loaded sentence that avoids filler and gets the core transaction out quickly. It is appropriately sized for a simple purchase, though it could have used the spare space for behavioral context.

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 a rich input schema, output schema, and annotations, the minimum facts are present, but the lack of usage guidance and payment-flow explanation in the description leaves the agent to assemble context from the schema. It is minimally viable but not fully self-contained.

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 wallet and paymentProof already have descriptions; the tool description contributes no parameter-level semantics. At baseline 3, it is adequate but adds no extra guidance 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?

Description uses a concrete action ('Buy') with a quantity and resource ('1000 prompt-injection scans'), so an agent knows the transactional nature at a glance. It is not tautological and no sibling tool is similar, but it doesn't explicitly state when it differs from any alternative, stopping short of a 5.

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?

No sentence addresses when this tool should be used or when an alternative would be preferable. The only secondary phrase, 'Omit to receive a 402 price quote,' is parameter behavior, not usage context. The agent must infer the intended use from the name alone.

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