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

Annotations declare destructiveHint=true and idempotentHint=true, but the description adds the concrete mechanism behind that: omitted fields keep their values, empty strings clear them and may invalidate checkout, and clearing phone makes validation fail. It also discloses the OAuth scope (checkout:write) and that buyer/order state changes, which annotations cannot express.

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?

Five short sentences, each carrying distinct load: mutation semantics, clearing/validation consequences, workflow ordering, scope + non-submission guarantee, and state impact. The most consequential constraint (state changes, does not pay or submit) is stated up front rather than buried.

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?

For a 7-parameter mutation tool with an output schema, this covers everything an agent needs: input sourcing, clearing behavior, validation dependency, required auth scope, and the fact that it neither pays nor submits. Return values are correctly left to the output schema.

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 per-field meaning is already documented, including the omission/clearing rules. The description still adds a cross-reference the schema does not contain — that payment and delivery values must come from get_checkout options — which is real value for the two enum 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?

States a specific verb and resource ('Change one or more checkout fields') and immediately distinguishes itself from siblings by naming get_checkout as the source of valid choices and by excluding prepare_order and submit_order. An agent can pick this tool over the four other checkout-adjacent tools without opening a schema.

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 explicit ordering ('Read validation before prepare_order'), explicit exclusions ('neither submits an order nor makes a payment'), and names the sibling that supplies enum values ('choices from get_checkout'). This is a full when/when-not/alternative specification.

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