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

The description discloses return behavior ('Returns a widget with the cart items and a working checkout link') and explains the two operational modes. Annotations already cover readOnly=false and destructiveHint=false, so the description adds value by specifying the output and the auto-recommend behavior of query mode. It does not discuss rate limits or side effects, but these are not hinted at by annotations.

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 three sentences with clear structure: purpose, mode list, exclusion, and return output. No redundant phrases or filler. It is front-loaded with the primary purpose and efficiently conveys all necessary pointers.

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 3 parameters, no required fields, and no output schema, the description covers the essential context: what it does, when to use, modes, and output. Minor gaps include not specifying behavior when both query and products are provided (though schema handles that) and absence of error-case handling, but these are partially covered by the schema and not critical for selection.

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?

Input schema has 100% parameter coverage, so the baseline is 3. The description adds meaningful context by explaining the conditional relationship: products array is for 'specific product names' while query mode 'auto-recommend[s] and cart[s]', and that query is 'only used if products array is not provided' (though that detail is also in the schema). This helps the agent choose between mutually exclusive parameters.

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 explicitly states the tool's purpose with a specific verb and resource: 'Create a buyable shopping cart with a real checkout URL.' It also distinguishes itself from siblings like search_products and skincare_recommend by clarifying it's for cart creation, not browsing or recommending.

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 when-to-use and when-not-to-use guidance: 'Do not use for browsing or recommendations — use search_products or skincare_recommend first.' It also details two distinct modes ('Pass products array' vs 'Pass query string') and conditions for each, aiding correct invocation.

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