Create a product variant

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

Beyond the mutation implied by readOnlyHint=false, the description discloses important behaviors: options missing from the product are auto-created, prices are integers in the smallest currency unit and default to the store currency, and the created variant is returned. It does not address failure modes like duplicate variants, but the annotations already cover the mutation/safety profile.

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?

Three tight, front-loaded sentences cover the action, key variant-option behavior, price rules, and return value. There is no filler or repetition of the title, and every sentence contributes operational guidance.

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 an 8-parameter mutation with no output schema, the description covers the highest-risk semantics: option completeness/auto-creation, integer price units, currency default, and return value. Defaults for title and inventory are left to the schema, which already documents them, so the definition is adequate 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 100%, so the baseline is 3. The description mostly restates what the schema already says about options and prices, such as 'provide a value for every option the product already has' and integer prices. It adds little new meaning beyond the structured parameter descriptions.

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 opens with a specific verb and resource: 'Add a variant to a product along one or more option dimensions,' which clearly states what the tool does. The mention of option dimensions and auto-creation of missing options distinguishes it from product-level create tools and from batch variant updates.

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 gives clear usage context: variants are added along option dimensions, missing product options are created automatically, and callers must provide values for every existing product option. It does not explicitly name alternatives such as updateProductVariantsInBatch or state when not to use this tool, so it stops short of a 5.

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