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

With no annotations, the description carries the full disclosure burden. The verb 'check' and phrase 'currently sellable and available' convey that this is a read-style status query, adding meaning beyond the name. However, it doesn't disclose output format, errors, or any side-effect guarantees, leaving some behavioral details implicit.

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?

Two short sentences, each earning its place: the first states the action, the second the usage context. No filler or repetition; the most valuable information is front-loaded.

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 simple two-parameter read tool, the description covers purpose and usage well, but it omits the return shape (e.g., boolean vs stock count) and leaves site_slug undocumented. Since there is no output schema to fill that void, an agent has to guess at the result format.

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 0%, so the description must compensate, but it only implicitly maps to variant_id via 'selected product variant'. site_slug is never mentioned or explained; the agent must infer its meaning from the parameter name alone. This is a clear gap for a tool with zero schema documentation.

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 uses a specific verb ('check') and resource ('selected product variant') and clarifies the exact condition being tested: sellable and available. It clearly distinguishes this check from sibling cart and search tools, which operate on different resources or actions.

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 second sentence gives explicit guidance on when to call: 'when availability matters or immediately before adding a selected variant to a cart.' It does not mention alternatives or when not to use, but the context is clear enough for an agent to select it appropriately.

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