update_cart_item

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

With no annotations, the description carries the full burden. It adds one useful behavioral trait (quantity=0 removes the item), but says nothing about auth requirements, what happens with an invalid line_item_id, or quantity bounds. For a mutation tool with zero annotation coverage this is a significant gap.

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-loaded with the action, then a short Args list with no wasted text. Efficient, though the Args entries for cart_id/line_item_id add little beyond restating the names.

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. As a 3-param mutation with no annotations, it is minimally adequate but leaves permissions, failure modes, and quantity constraints unaddressed.

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 0%, so the description must compensate, and it does document all three parameters. However, cart_id and line_item_id are restated near-tautologically, and only quantity ("0 to remove") adds real meaning. It covers the params but thinly.

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 ("Update the quantity of an item in the cart"), which an agent can distinguish from siblings like add_to_cart and remove_from_cart. It does not explicitly name those siblings, but the operation is unambiguous.

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 rather than spelled out. The parenthetical "(0 to remove)" is the one piece of routing guidance, hinting this overlaps with remove_from_cart, but there is no explicit when-to-use/when-not statement or named alternative.

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