Add to cart

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

With no annotations provided, the description must carry the burden of behavioral disclosure. It states that the user ID comes from the JWT subject, which is a useful constraint, but it does not reveal other behavioral aspects: whether adding an existing item increases the quantity or creates a duplicate, what happens on failure, or any side effects beyond the implicit write operation.

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?

The description is exceptionally concise, consisting of two sentences with no redundancy. It front-loads the primary action and follows with the key constraint, both of which are instantly actionable. Every word 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 tool with 8 parameters and no output schema, the description is thin. It does not cover how the system handles duplicate items, what happens when quantity exceeds limits, or how the cart is confirmed. The presence of a sibling tool like update_cart_item makes it crucial to clarify behavior when adding an already existing item, which is not addressed.

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?

The schema provides descriptions for all 8 parameters, including the origin of item_id and the optional fields. The description adds minimal extra meaning beyond the schema, but even with full schema coverage, it does not explain the purpose of snapshot fields like title or unit_price in this context, which remains at baseline.

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 clearly states the action (add a product to the authenticated user cart) and names the resource (cart). It is distinct from siblings like view_cart or update_cart_item, though it does not explicitly differentiate itself, making the purpose easily discernible.

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 lacks guidance on when to use this tool versus alternatives. It mentions that the user ID comes from the JWT subject, but does not explain when to prefer add_to_cart over update_cart_item or how to handle existing cart entries. There is no mention of exclusions or alternative scenarios.

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