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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds auth context beyond the annotations ('No account needed') and previews the return payload, which is useful operational detail the structured fields do not provide.

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?

A single dense sentence with the core action and return contents front-loaded, and the usage cue last. The format enumeration (UGC, talking head, unboxing...) is somewhat long but demonstrates catalogue breadth, so it largely earns its space.

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 listing tool with an output schema and full annotation coverage, the description supplies everything needed: what it lists, what each entry contains, that no account is required, and when to call it.

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 (0 params, empty schema), so the baseline is 4. The description correctly implies there is nothing to supply and instead characterizes the payload rather than inventing parameter semantics.

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 actual catalogue contents, so an agent knows exactly what comes back. It is clearly distinguishable from sibling lists (list_models, list_canvases, list_brand_profiles) and is tied to the ad-writing workflow.

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?

'Pick one before writing a brief' explicitly places the tool in the workflow and signals the downstream consumer (write_ad_storyboard / generate_ad). It gives clear context but names no alternative tool or exclusion condition, so it stops short of a 5.

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