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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world, so safety is covered. The description adds value beyond that by disclosing return contents (engines, costs, sizes, characters) and the "call once" caching implication. With no output schema, the return description could go further on response shape or staleness.

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, zero filler; the capability enumeration is front-loaded and the operational instruction comes last. The dense list format efficiently conveys the breadth of the return value.

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 no output schema, the description carries the burden of telling the agent what comes back, and it does so at a category level (engines, costs, sizes, looks, song/lyric/character types). Anything more detailed would be guesswork, but a hint on structure (e.g., grouped by product type) would fully close the gap.

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?

Zero parameters, so there is nothing to disambiguate and the description correctly spends no words on arguments. Baseline 4 applies for a no-arg tool.

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?

Names a definite resource (this account's creative capability catalog) and enumerates its contents concretely: video engines with lengths/resolutions/shapes, image sizes and looks, edits, songs, lyric/music videos, characters, Remake. An agent can distinguish it from get_account (account facts) or list_characters (one collection) purely from this sentence.

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 an explicit directive: "Call it once at the start to know the full creative range to offer" — establishing both timing and cardinality, which is unusual and useful guidance. It doesn't name an alternative for the case where an agent only needs one sub-collection (e.g., list_characters vs. this), so there is no explicit exclusion.

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