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

The annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the mutation profile is covered. The description adds the meaningful prerequisite that a plan must exist, but says nothing about duplicate items (despite non-idempotency) or what happens if the plan is missing.

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 with the action front-loaded and the prerequisite trailing. 'The week needs a plan' is terse to the point of being slightly cryptic, but nothing is wasteful.

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 simple four-parameter mutation with full schema coverage and annotations, the description covers the core behavior but omits failure behavior when no plan exists and duplicate-item handling, both relevant given non-idempotency and no 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 description coverage is 100%, so the schema already explains all four parameters, including that weekStart can be any date in the target week. The description's phrasing mirrors the schema rather than adding format or edge-case guidance.

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 gives a specific verb and resource ('Add one item to the shopping list') and scopes it to the week containing weekStart. It implicitly contrasts with remove_shopping_item and check_shopping_item via 'Add one item,' though it never names a sibling explicitly.

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 week needs a plan' states a prerequisite, which is genuine usage context. However, it does not say when to prefer this over adjacent tools like add_inventory_observation or wish_dish, nor what to do when no plan exists.

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