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

Annotations already declare the write, idempotent, non-destructive profile, so the description's added value is the payment-rail detail and the fact that payment_data is a signed proof. It does not explain the effect of finalizing (does it produce an order?), what happens on payment failure, or how idempotency behaves on retry — meaningful gaps for a settlement mutation.

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 short sentences, purpose front-loaded before the example. The example earns its place by showing the argument shape, though it is close to redundant given the schema.

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?

Output schema and annotations cover the return shape and safety profile, and parameters are fully documented. What remains missing is the invocation precondition (checkout state) and the rail/payment_data relationship, which an agent needs to call this successfully.

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 coverage is 100%, so both parameters are already documented, and the example merely echoes checkout_id. The description adds no detail on payment_data structure or whether it is required per rail, which matters because required-parameters is 0 and the object is nested.

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?

States a specific verb and outcome ("Finalize checkout settlement") plus the concrete payment rails it supports (Base USDC x402, Stripe MPP), which clearly separates it from update_checkout and cancel_checkout. It never explicitly names a sibling, so it stops short of full differentiation.

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 only usage signal is a single example call. There is no statement of when to use this versus update_checkout, no prerequisite that a checkout must exist and be in a payable state, and no guidance on choosing between the two payment rails.

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