add_to_cart

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

With no annotations, the description carries the burden and does well by disclosing that authentication is required and that productId/price must be sourced from search/list products. It also clarifies its behavioral role (add vs. increase). However, it doesn't reveal potential side effects (e.g., failure behavior) or whether quantity is absolute/incremental beyond the schema's 'Target quantity to set'.

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 concise and well-structured: the primary action is stated first, followed by usage boundaries, alternatives, auth, and data sourcing. Every sentence serves a purpose without redundancy.

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?

The description is complete for a moderately complex tool: it covers purpose, alternatives, authentication, and parameter provenance. It doesn't mention error handling or return values, but there is no output schema, and these are not essential for selecting/invoking the tool correctly in most cases.

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 100%, so the baseline is 3. The description adds value by telling the agent where to obtain productId and price ('Get productId and price from search_products or list_products'), which is not in the schema. It also reinforces the quantity parameter's intent with the 'bumping qty' example, though the schema already describes it as a target quantity.

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 tool's function with a specific verb and resource: 'Add a NEW product to the basket or INCREASE the quantity of an existing product.' It also explicitly distinguishes itself from sibling tools by naming remove_from_cart and add_flash_deal_to_cart for alternative use cases.

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 explicit usage boundaries: 'Use this only when the quantity is going UP' and gives concrete examples. It also names the exact alternatives for decreasing/deleting (remove_from_cart) and flash deals (add_flash_deal_to_cart), fulfilling the when/when-not guidance.

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