ue_add

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

With no annotations, the description carries the full burden and does well: it declares this is a write action, that the cart is scoped per store while multiple carts may coexist, and that adding is not purchasing and requires user confirmation. It stops short of saying what happens on failure (item unavailable, option mismatch) or whether the response returns the updated cart.

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?

Front-loads the action and its write nature, then parameter semantics, then two short bullets with genuinely non-obvious constraints. Every sentence adds information an agent would otherwise have to guess; nothing is padded.

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 3-parameter write tool with no annotations and no output schema, the description supplies the mutation semantics, the cart-per-store model, the confirmation workflow, and the verification tool to call next. That is enough for correct invocation without further discovery.

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 a baseline of 3 would apply, but the description goes beyond it: it explains the spec string as space-separated keywords, one per option group, matched level by level, with concrete examples in two languages ('Coke Large' / 'コーラ ポテト(L)'). That materially disambiguates a free-text parameter the schema only labels '选项关键词，空格分隔'.

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 ('Add one item to the cart') and immediately qualifies it as 'a write action', which separates it from read-only siblings like ue_search/ue_cart. The closing note 'Adding is not buying' implicitly draws the boundary with ue_place, so an agent can place the tool without opening other schemas.

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?

Explicitly routes the agent to ue_cart for post-add verification and instructs 'Confirm with the user before adding anything', which is meaningful pre-use guidance for a mutating tool. It does not, however, state how to obtain the required id (that guidance lives only in the parameter schema, pointing at ue_store).

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