Update variant

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

With no annotations, the description carries full burden and excels: it discloses that null values are rejected before any call, that no field is nullable, and that the variant must not be empty. This goes beyond schema details.

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 compact sentences, each earning its place. The core action and method are front-loaded, and the alternative guidance is presented efficiently.

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 tool with a nested merge-patch object and no output schema, the description covers key constraints, validation behavior, and points to get_operation_schema for exact shape. It also addresses the edge case of clearing prices, making it highly complete.

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 100%, so baseline is 3. The description adds meaningful behavior: 'send only the fields to change' and 'Must not be empty', plus the null rejection context, which enriches parameter understanding.

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 verb and resource: 'Update an existing variant via JSON Merge Patch', with concrete field examples (pricing, stocks). This distinguishes it from sibling tools like bulk_update_prices.

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?

Explicitly states when to use (partial updates) and provides an alternative for a specific case: 'to clear a price, use bulk_update_prices'. Also directs to get_operation_schema for exact shape, giving solid guidance.

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