add_to_cart

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

No annotations are provided, so the description carries the full behavioral burden. It implies a mutation but says nothing about auth requirements, errors when the cart is invalid, or whether re-adding the same item merges quantities or creates a duplicate line.

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 purpose sentence is front-loaded, followed by a compact args list with zero filler. Slightly list-like, but every line 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?

An output schema exists, so return values needn't be explained, and all params are covered. However, for an unannotated mutation tool it leaves gaps around failure modes and prerequisites beyond the implicit 'existing cart' hint.

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 0%, so the description must compensate, and it largely does: it documents all five params including defaults (quantity 1, special_instructions '') and the options shape {id, quantity}. The options object type is left loosely described but the added meaning over the bare schema is substantial.

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+resource: 'Add an item to an existing cart.' The qualifier 'existing' implicitly separates it from create_cart, though no sibling is named 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?

'Existing cart' implies the cart must already exist (via create_cart/get_cart), which is useful implied guidance, but the description never names alternatives like update_cart_item or remove_from_cart, nor states when-not to use it.

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