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

Annotations are sparse (all hints false), so the description carries the burden. It discloses that the tool itself does not render anything ('renders nothing itself') and that it delegates to other tools, which is important behavioral context. It goes beyond the annotations by clarifying the division of labor. However, it does not disclose whether the downstream calls (generate_image, score_ad) produce side effects or what the final output format is, so some transparency is lacking.

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 description is two sentences, front-loaded with the main action and outcome, and then names the downstream tools. Every word earns its place: it states what the tool does, what it produces, and what it doesn't do. No redundancy or filler.

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 planning tool with no output schema, the description gives a strong sense of what the agent can expect: it produces variants with headline and visual brief, then hands off to generate_image and score_ad. It does not specify the exact return format or how the plans are surfaced, but given the delegation model and the fact that the tools it calls are explicit, this is reasonably complete. The description covers the purpose, the workflow, and the limitation, which is sufficient for correct invocation.

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 description coverage is 100%, so all four parameters (brand, count, product, language) are already described in the schema. The description adds conceptual context (e.g., 'N DISTINCT' and 'headline + visual brief') but does not add specific parameter-level detail beyond the schema. Since the schema fully documents parameters, the baseline of 3 is appropriate; the description adds marginal value by tying parameters to the overall workflow.

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 states a very specific action: fan a brief into N distinct ad angles with specific components (headline + visual brief), then delegates to generate_image and score_ad. It clearly distinguishes itself from siblings like plan_ad, mine_angles, and render_ad by emphasizing 'LLM planning only; renders nothing itself.' The verb-resource pairing is unambiguous.

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 provides clear context for when to use the tool: it is for planning ad variations before rendering/scoring. It explicitly mentions the downstream tools (generate_image and score_ad) and declares it is 'LLM planning only', which implies it should be used instead of direct rendering tools. However, it does not explicitly name alternatives or state when not to use it, leaving some ambiguity for an agent comparing against similar planning tools like mine_angles or plan_ad.

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