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

Annotations already declare readOnlyHint=false, destructiveHint=true and idempotentHint=true, so the mutation profile is covered. The description adds genuinely new context: the required OAuth scope (checkout:write), the fact that no order is sent and no payment is made, and that buyer or order state changes. It does not explain the destructive dimension implied by clearing fields, which lives only in the schema.

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?

Three short sentences, front-loaded with the action and scope, followed by the negative constraint and the auth/state note. Every sentence carries distinct information and nothing is repeated from 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?

An output schema exists and the input schema is exhaustive, so return values and per-field semantics need no duplication here. Combined with the annotations, the description covers action, scope, side-effect limits and auth; only a note that at least one property must be supplied (schema's minProperties) is absent, which is a minor gap.

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 each parameter's keep/clear semantics, max lengths and enums are already fully documented in the schema. The description only summarises the field families (delivery, payment, contact), adding no syntax or format detail beyond what the schema provides; baseline 3 applies.

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 (Update) and resource (the buyer's delivery, payment or contact choices in the existing checkout), and explicitly scopes it to an existing checkout rather than order creation. The clarifying clause 'Does not send an order or make a payment' cleanly separates it from submit_order and prepare_order among the siblings.

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?

Gives a clear when-not: it does not send an order or make a payment, implicitly routing order submission to submit_order. It also implicitly depends on choices from get_checkout (the enum descriptions reference get_checkout options). It never names the alternative tools outright, so it falls short of an explicit routing rule.

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