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

Beyond the annotations (readOnly=false, destructive=false, non-idempotent), the description discloses the cost model ("Bills as one image generation") and a real side effect the annotations do not cover: passing brandId switches the key's active brand like use_brand. It does not describe the return value or whether results arrive sync vs. via a job, which would be the remaining useful behavior to state.

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 core action, and every clause carries information (what is preserved, what is replaced, the alternative tool, the billing unit). It is somewhat dense with parentheticals and caps emphasis, which costs a little readability, but there is no filler sentence.

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 two-param generation tool with no output schema, the description covers inputs, output character, cost, side effects and the sibling alternative, which is nearly everything needed. The one gap is how the generated image is retrieved (immediate result vs. job lookup via get_job/list_jobs), which is left unstated.

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%, so the baseline is 3, but the description genuinely adds meaning for brandId by noting it changes this key's active brand (as use_brand does) — a consequence not present in the schema. The imageUrl note merely restates the schema's own wording, so there is no bonus there.

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 verb and resource ("One-click STATIC-AD CLONE") and states exactly what is produced: an on-brand rebuild preserving layout, composition and energy with all source-brand traces removed. It also distinguishes itself from near-neighbours by scope (IMAGES ONLY, use clone_video for video), so an agent need not open sibling schemas to choose.

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?

It gives an explicit exclusion and the alternative to use instead ("IMAGES ONLY — for a video ad use clone_video with its link, then render_ad"), plus the condition for targeting a brand ("pass brandId to target a specific brand") and the default (omit to use active brand). Both when-to-use and when-not-to-use are stated.

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