ucp_checkout_complete

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

No annotations are provided, so the description must cover behavioral traits. It states 'finalizes the purchase' (a write operation) and lists returns, but does not disclose idempotency, failure behavior, side effects, or required permissions.

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 has a clear Args/Returns structure, but it redundantly lists all parameter descriptions which are already explained. Slightly verbose but still well-organized.

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 an output schema exists (context signals confirm), the description adequately covers inputs and returns. However, it lacks details on error handling, idempotency, and edge cases.

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 has 0% description coverage, but the description fully explains each parameter's purpose (e.g., 'merchant_url: The base URL of the UCP-enabled merchant'). This adds substantial meaning beyond the raw 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 clearly states the tool completes a checkout session by submitting payment and finalizing the purchase. It uses a specific verb ('complete') with a clear resource ('checkout session'), and is distinct from sibling tools like create, update, or discover.

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 implies this is the final step in the checkout process but does not explicitly state when to use it versus alternatives (e.g., update or create). No guidance on prerequisites or when not to use.

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