ht_update_cart_item

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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the write/idempotent/safe profile is covered structurally. The description adds genuine value with 'Quantity 0 removes the item' and 'Nothing is ordered or charged', clarifying that this mutates only the cart and never places an order. It still says nothing about what happens on an unknown UPC, out-of-range quantity, or what the call returns.

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 sentences, front-loaded with the operation, then the edge case, then the safety reassurance. Every sentence adds information and none is padding.

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 single top-level parameter that nests item objects, the description covers purpose, the terminal quantity case, and the no-order/no-charge guarantee, which is close to what an agent needs. Missing are multi-item behavior (up to 50 items applied in one call) and any note on partial failures, but with no output schema these are modest gaps.

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?

Reported schema description coverage is 0%, so the description carries weight; it does add meaning by flagging substitution preference as a settable attribute and by defining quantity 0 as removal. It says nothing about the other quantity bounds (max 99) or the array-size limit (min 1, max 50), and the substitution policy enum meaning is left entirely to the schema.

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 (set) and resource (quantity/substitution preference of items already in the Harris Teeter cart), and the phrase 'already in the cart' implicitly separates it from ht_add_to_cart. It does not name ht_remove_from_cart even though 'Quantity 0 removes the item' overlaps with it, so sibling differentiation is present but not explicit.

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?

Usage is implied by 'items already in the cart' and the 0-means-remove rule, which tells an agent how to effect a removal here. However, it never says when to prefer ht_remove_from_cart, and it gives no prerequisites (e.g., cart must already contain the UPC) or failure conditions.

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