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

The description adds valuable behavior beyond the provided annotations (readOnlyHint, openWorldHint) by stating 'Live, never cached,' which informs the agent about data freshness. It also warns about the correct encoding of variant_ids, which is a behavioral constraint. No contradictions with annotations exist.

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, with every sentence serving a purpose. It front-loads the main use case and includes essential operational details (array of strings, live data) without redundancy. It is well-structured and easy to parse.

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 tool has moderate complexity with 6 parameters, and while the core required parameter is well explained, the optional parameters are not addressed. There is also no output schema, and the description does not mention what the tool returns. However, for a simple read-only inventory check, the essential context is covered, but gaps remain for a fully self-sufficient description.

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?

The description significantly clarifies the required parameter variant_ids with a precise type, example, and a warning ('Never send variant_ids as numbers'). However, the schema description coverage is only 17%, and the description does not compensate for the other five parameters (journey_id, match_type, selected_sku, result_set_id, selected_handle), leaving their semantics unclear.

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 purpose: 'confirm stock before recommending a SKU or building a cart.' This specifies a verb, resource, and use context. However, it does not explicitly distinguish itself from the sibling tool 'inventory_status', which may serve a similar function, so it does not fully meet the top criterion for sibling differentiation.

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?

It provides clear context for when to use the tool: 'before recommending a SKU or building a cart.' It also specifies a key requirement ('Required argument'). However, it does not mention any exclusions or alternative tools, so it stops short of full guideline completeness.

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