quick_buyOne-step purchase for products with instant checkout enabled (seller opt-in) and orders under bulk threshold. For products without instant checkout or larger orders, use request_quote instead.
| Name | Required | Description | Default |
|---|---|---|---|
| quantity | Yes | Number of units to purchase | |
| buyer_name | No | Buyer's full name | |
| product_id | Yes | Product ID (format: product_123) | |
| buyer_email | Yes | Buyer's email address | |
| buyer_company | No | Buyer's company name |
Changes observed during successful MCP inspections.
Input schema / properties / shipping_countryRemoved value: -{
- "description": "Two-letter country code (e.g., US, GB)",
- "type": "string"
-}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description adds that the purchase is one-step and depends on seller opt-in, but it does not disclose side effects like immediate charge, order confirmation, or whether the purchase is irreversible. Annotations only indicate non-read-only and non-idempotent, so more behavioral context would help.
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 concise sentences with no redundancy; the primary use case is front-loaded and the alternative is given in the second sentence. Every clause earns its place.
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?
The description covers eligibility and alternatives well, but with no output schema, it does not tell the agent what to expect after a purchase (order ID, confirmation, or error behavior). This is the main missing piece for a side-effecting transaction tool.
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 all parameters are already documented in the schema. The description itself adds no parameter-level meaning, which is acceptable at the baseline.
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 names a specific action ('One-step purchase'), a clear resource (products with instant checkout enabled and under bulk threshold), and contrasts with request_quote. This distinguishes it from siblings without requiring schema access.
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?
It explicitly states the conditions for quick_buy (instant checkout enabled and under bulk threshold) and the fallback to request_quote for products without instant checkout or larger orders. This is direct when-to-use/when-not-to-use guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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