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

With no annotations, the description carries the full burden of behavioral disclosure. It does state that the action is additive ('Add') and that it returns the updated basket, which is meaningful. However, it does not mention whether duplicate variants are merged or added separately, any permission requirements, or error behavior. This is adequate but not rich.

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, focused sentences. The first sentence states the core action, the second provides a dependency hint, and the third states the return value. No words are wasted and the most important information is front-loaded.

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?

Given the tool's simplicity num (3 flat params, no nested objects, no output schema), the description covers the essential guidance: what it does, where to source the ID, and what it returns. It omits edge-case behavior like quantity handling or basket ownership validation, but those are minor for a straightforward cart-add operation.

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 every parameter already has description text in the schema. The tool description adds only a cross-reference to get-product for variant_id and implies the basket_token comes from create-basket. This is complementary but does not go beyond the schema, so the 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?

The description immediately states the specific action ('Add a product variant to a basket'), which clearly distinguishes it from sibling tools like remove-from-basket, update-basket-item, and view-basket. It also references a companion tool (get-product) for obtaining variant IDs, reinforcing its specific role.

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 description provides clear context by telling the agent to obtain variant IDs from get-producticket and implying this is the tool for adding new items. It does not explicitly state when not to use it, nor does it contrast with update-basket-item, so it falls slightly short of a full 5.

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