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

Adds real context beyond the annotations: available is absolute rather than a delta, trackInventory without available leaves a variant unsellable, and POD/digital variants are rejected. What it omits is equally important for a destructiveHint=true tool: whether variants not listed in the array are left alone or wiped.

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?

Four tight sentences, front-loaded with what the tool does, then the two operational traps. No filler, no restating of the title or schema types.

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 destructive mutation with no output schema, it covers the important failure modes (refusals, unsellable state) but not the replacement semantics of the variants array. An agent still cannot tell whether omitting a variant clears its stock, which matters before invoking a destructive tool.

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 0%, so the description must carry the load, and it does for the hardest fields: optionValues semantics (empty array for no-option products) and available as an absolute count. It leaves continueSellingWhenOutOfStock and the 1–250 variants bound unaddressed, but the core addressing model is explained.

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?

States a specific verb and resource: setting stock counts and stock policy for a Replo-managed product's variants. The variant-addressing scheme (option-value combination) makes the scope precise. It does not explicitly contrast with the sibling update_product, which an agent might reasonably confuse with this tool, so it falls short of a 5.

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?

Gives a clear when-not rule: only merchant-fulfilled products can track stock, and print-on-demand/digital variants will be refused. It also warns to set trackInventory and available together. It does not name an alternative tool for the refused cases, so there is no explicit routing to a sibling.

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