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

Annotations already declare non-read-only, non-destructive, non-idempotent; the description adds genuinely new behavior: no credits are consumed, no new file is produced, and the copy becomes the target set's picked version, which implies a state change on the destination set. It does not say what happens if the destination set already has a picked version, leaving a meaningful side effect underspecified.

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 core operation, its constraints and the cost model are front-loaded in one sentence, followed by a single clarifying note. The trailing example is largely redundant with the input schema but takes only a line and does not obscure the purpose.

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 two-parameter copy tool with annotations present, the definition covers purpose, cost and destination constraints adequately. With no output schema, however, it never indicates what the call yields (e.g. whether a new generation identifier is returned), nor how an existing picked version in the target set is handled.

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 parameter meaning. It partially does by tying image_set_id to the same product/platform/language constraint, but the example JSON only echoes the two field names and never explains that generation_id identifies the source finished image rather than the destination.

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 precise verb and resource (copies a finished image into another image set) plus the hard constraints of the operation (same product, platform and language). The 'Free: the same file' clause distinguishes it from generation siblings like generate_image_set or regenerate_image, so an agent can tell it apart without opening the schema.

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 concrete use case (build variant B of an A/B test) and an implicit precondition that the target set must share product, platform and language. It does not name an alternative such as pick_image_version or generate_image_set for when this is the wrong choice, so it stops short of 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.