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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavior: results are limited to the 10 most recent confirmed orders, ordering is newest-first, and scoping depends on auth mode (connected consumer sees own orders; agent key without externalReference cannot resolve ownership). Return format is enumerated, though pagination/absence of older orders isn't discussed beyond the cap.

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 tight sentences with the scope limit and returned fields front-loaded, followed by auth and the hand-off to reorder. Dense but every clause carries information; the parenthetical slightly burdens readability but earns its place.

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 single-parameter read tool with no output schema, the description covers scope, ordering, returned fields, auth-dependent behavior and the follow-up action. Nothing an agent needs to call it correctly is missing.

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% and the single parameter is documented there, so baseline is 3. The description goes further by tying externalReference to the id sent in create_cart and stating the consequence of omitting it under agent keys, which the schema states only partially.

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 plus precise scope: last confirmed orders, up to 10, newest first, with the fields returned (store, items, total, date, cartId). It is clearly distinguishable from siblings like reorder and create_cart, which are named with their roles.

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?

Explains the purpose (offering a repeat purchase), names the alternative (reorder with the cartId) and gives the condition that selects it. It also states the two authentication modes and what each requires, which is exactly the guidance an agent needs before calling.

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