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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's job is to add context, which it does: newest-first ordering, the exact facets reported per version, and the credit cost of the adjacent actions an agent will likely take next. It stops short of saying what happens with an unknown photoId or an empty version list.

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 sentences, front-loaded with the returned facets and followed by the sibling routing. The long comma-delimited list of return fields is dense but each item carries information; no filler or restatement of the title.

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?

With an output schema present, the description needn't re-specify return structure, and annotations plus full schema coverage handle the rest. What's missing is minor: behavior on an invalid photoId or a shot with no saved versions, which an agent might reasonably want to know.

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% and both parameters are fully documented in the schema, including that photoId accepts a play position like "shot 3" and listingId comes from list_listings. The description adds only the loose notion of 'one shot' and no extra syntax or constraints, so the baseline of 3 applies.

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 names a specific resource ('Every AI+ version saved on one shot') and enumerates exactly what is returned: version number, what generated it (prompt or VFX), which version is currently playing, length fit, and rating. That is specific enough to separate it from use_ai_version and regenerate_ai_version, which are named in the same breath.

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 routes the agent to the right sibling: switching to an existing version goes to use_ai_version (no credit), creating one goes to regenerate_ai_version (1 credit). This is clear when-to-use-what guidance, though it doesn't state an explicit precondition or a case where this tool should be skipped (e.g. no versions exist yet).

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