purchase_marketplace_product

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions previewing or purchasing and using operation_id, but it does not disclose the payment workflow, the requirement for a buyer wallet, the x402 invoice steps, or the fact that this tool may trigger a financial transaction. The schema hints at these behaviors (auto_pay, tx_hash, payment_signature), but the description itself is silent on the most consequential behavior: charging money.

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 sentences, front-loaded with the critical usage context ('Use after find_marketplace_products'). Every clause earns its place: the action, the resource, the key parameter, and the contrast with the sibling. No wasted words.

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?

This is a payment-related tool with 8 parameters, nested inputs, and no output schema, yet the description provides almost no guidance on the overall flow: how preview differs from purchase, what inputs are expected, how to obtain tx_hash/payment_id, or what happens after payment. An agent would need to infer the payment protocol entirely from parameter names. The description is too sparse for the tool's complexity.

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 baseline is 3. The description adds meaning only to operation_id by explaining it comes from find_marketplace_products. It does not elaborate on the payment-related parameters (preview, auto_pay, tx_hash, payment_id, payment_signature) or how they interrelate, but the schema already documents each parameter individually.

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 states a specific verb ('Preview or purchase'), a clear resource ('selected paid product'), and the exact mechanism ('by its operation_id'). It also distinguishes itself from the sibling by noting it avoids searching the full dynamic tool list, so an agent can immediately tell this is the follow-up action after find_marketplace_products.

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 explicitly says 'Use after find_marketplace_products', which establishes the intended sequence and context. It also implies the alternative (find_marketplace_products) and clarifies that this tool is for the already-selected product. However, it does not explicitly state when NOT to use it, such as when the product has not been selected or when a different payment method is required.

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