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

Annotations already provide readOnlyHint and openWorldHint. The description adds valuable behavioral context with 'Live, never cached,' which is not in the annotations. It also warns against sending variant_ids as numbers, which is a behavioral constraint beyond the schema. No contradictions.

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: it starts with the use case, then the required argument with an example, then a critical warning, and finally the live behavior. Every sentence earns its place and there is no fluff.

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?

Given that there is no output schema and multiple optional parameters, the description adequately covers the primary usage with the required variant_ids and the live data behavior. It does not explain what the tool returns (e.g., stock status format) or the purpose of optional parameters, but the core scenario is sufficiently specified for correct invocation.

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 description coverage is only 17%, so the description must compensate. It does explain variant_ids format and strongly warns against sending numbers, which matches the schema description but adds emphasis. However, the other 5 optional parameters (journey_id, match_type, etc.) are completely unmentioned, leaving the agent without guidance on their semantics.

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 is a specific verb+resource with a concrete use case. However, it does not explicitly differentiate from the sibling tool 'inventory_status', which likely has similar functionality.

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 gives clear context for when to use the tool ('before recommending a SKU or building a cart') and provides a critical usage requirement for variant_ids. It does not mention when not to use it or name alternative tools, so it misses the full '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.