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

No annotations provided, but the description details key behaviors: stock reservation for 5 minutes, return of non-final data, requirement for same shop, and the need for a subsequent signed challenge. It lacks info on idempotency or error handling, but covers the main behavioral traits beyond basic read/write hints.

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 four sentences, each contributing essential information: action, returns, next step, and constraints. It is front-loaded with the main purpose and avoids unnecessary words, making it efficient for an AI agent to parse.

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?

Given the tool's complexity (8 params, nested objects, no output schema), the description adequately covers purpose, workflow, return values, constraints, and the required follow-up action. It provides a complete mental model for an agent to use the tool correctly.

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%, but the tool description adds meaningful context for the 'shipping' and 'gift_recipient' parameters (conditional necessity based on cart contents) and reinforces the 'shop_id' constraint (all items same shop). This aids correct parameter usage beyond the schema's minimal descriptions.

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 specifies a clear verb ('実行する') and resource ('x402 チェックアウトの 1 回目'), and distinguishes it from the sibling 'submit_payment' by outlining the two-step process. It also details the returned data and constraints, making the tool's role unambiguous.

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 states when to use this tool (first step of checkout) and how it relates to 'submit_payment' (sign challenge and pass to it). It also provides conditional requirements for 'shipping' and 'gift_recipient' parameters, but does not exhaustively list when not to use it (e.g., if a reservation already exists).

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