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

With no annotations provided, the description carries the full behavioral transparency burden. It covers delivery timing, checkout flow, fee structure, self-purchase prohibition, strict PHI attestation requirements, and the 422 failure mode. This is unusually complete and actionable behavioral detail.

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 front-loaded with the primary purpose, then flows naturally into free/paid behavior and constraints. It is dense and could benefit from clearer segmentation, but every sentence adds meaningful operational detail. No irrelevant or filler content is present.

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 tool with no output schema and no annotations, this description provides a complete mental model: how to purchase, what happens after payment, when additional parameters are required, fee implications, and when the call will fail. The agent has enough to correctly call the tool and to plan follow-up with get_a purchase.

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?

The schema description coverage is high at 80%, so the description doesn't need to repeat parameter basics. It does add real value by explaining that buyer_attestation requires all five use-restriction affirmations to be true and by enumerating the buyer_intended_use categories. This goes beyond the schema's own descriptions. Only minor gaps remain around listing_id/email semantics, but those are covered by 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?

The description opens with 'Buy a listing in any vertical,' which states the specific action and resource. It does not explicitly differentiate this from sibling tools like bulk_purchase, but it clearly communicates the core operation.

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 concrete usage guidance: free listings deliver immediately, paid listings require Stripe checkout followed by polling get_purchase, and you cannot buy your own listing. It also explains special requirements for Personal Health Data listings. It does not explicitly mention alternatives such as bulk_purchase for multi-item purchases, but the context for using this tool is clear.

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