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

Annotations already cover readOnly, idempotent, non-destructive, closed-world behavior; the description adds auth context ('No account needed') not present in annotations, which is useful for an agent deciding whether it can call this early. It also previews the shape of each entry (one-line description, default aspect, shot count and duration), though the output schema likely covers much of that.

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?

Front-loaded with the action and resource, then the return contents and the ID-usage note in two short sentences. The format enumeration is illustrative rather than redundant, and no sentence is wasted.

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 zero-parameter read-only catalog tool with an output schema, the description supplies everything an agent needs: what is listed, what each entry contains, and how the IDs are consumed downstream. No missing prerequisites.

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?

The tool takes no parameters, so there is nothing to document; the baseline for a zero-parameter tool applies. The description correctly implies a full-catalog, unfiltered listing, which matches the empty schema.

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 ('See the ad formats the studio can produce') and enumerates the catalog contents (UGC, talking head, unboxing, tutorial, TV spot, etc.). This clearly separates it from sibling listing tools such as list_models, list_ugc_avatars and list_brand_profiles, which list different resources.

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 description gives clear context for use ('No account needed') and explains downstream relevance: 'A brief names one of these formats by its id,' implying this is a discovery step before writing a brief or generating an ad. It does not explicitly state when to prefer it over sibling catalogs, but the resource specificity makes the fit obvious.

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