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

Annotations already indicate destructiveHint=true and readOnlyHint=false. The description adds crucial behavioral details: the order is created UNPAID (status 'pending'), and the payment_url is a manual fallback. It also discloses that the agent must drive the subsequent payment flow, not stop here. This goes beyond annotations, providing complete transparency about side effects and required follow-up actions.

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 efficiently structured: the first sentence states purpose and key effect, the second lists requirements, and the rest is a clear, imperative note about the continuation flow. Every sentence serves a distinct, useful purpose. Despite length, it is front-loaded and easy to parse, with 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?

Given the tool's complexity (15 params, 12 required), the description covers the essentials: what it does, key requirements, and the critical follow-up steps. An output schema exists, so return values are handled. The description is complete enough for an agent to use the tool correctly, though it could mention error scenarios or prerequisites like a valid, non-empty cart.

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 input schema already documents all parameters with descriptions. The description adds modest context: it mentions that buyer_delegation_token comes from user auth and that a shipping address is required, but does not elaborate on individual parameter formatting or usage beyond what the schema provides. The baseline of 3 is appropriate; the description adds some value but is not essential for understanding parameters.

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 clearly states the tool's purpose: 'Execute checkout for a cart to create an order.' It specifies the action (checkout), resource (cart), and result (order). The title annotation 'Place order (checkout)' reinforces this. While sibling 'quick_checkout' exists, the description distinguishes by detailing requirements (delegation token, shipping address) and the unpaid state of the order. This provides sufficient clarity for selecting the tool.

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 preconditions: 'Requires a buyer delegation token (from user auth) and a shipping address.' It includes an IMPORTANT block that instructs the agent not to stop after checkout, but instead to continue the in-chat payment flow with specific next steps (get_payment_methods, initiate_payment, etc.). It even explains when to use the manual payment_url fallback. This is exceptionally clear guidance on when and how to use the tool vs. alternatives.

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