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

Annotations already declare destructiveHint=true, readOnlyHint=false and openWorldHint=true, so the agent knows this mutates external ad platforms. The description adds only the create-vs-update discriminator; it says nothing about what an update overwrites, whether updates are partial or full replacement, or what happens on partial batch failure across a multi-channel array.

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 short sentences, front-loaded with the resource and channels, with the create/update rule rendered in caps so it is impossible to miss. Nothing repeats and nothing 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 bulk, destructive, multi-channel mutation with 20+ nested per-channel fields, the description is thin on the things the schema cannot express: whether `ads_data` items are transactional, whether an update replaces unspecified fields, and whether COMPLETED vs DRAFT changes what is pushed upstream (buried in a nested field description). The exhaustive schema and annotations keep it from being inadequate, but real gaps remain.

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%, and the per-field docs are unusually detailed (CTA enums, per-channel length limits, required-for-channel markers, creativeID being a library ID not a URL). The description only restates the `id` semantics already documented in the schema, so it sits at the baseline rather than adding meaning.

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 specific verb pair (create/update), a specific creative type (IMAGE or GIF), and the exact channels supported (Facebook, Instagram, LinkedIn, Reddit). The media-type qualifier effectively separates it from siblings like create_update_video_ad or create_update_carousel_ad, but no sibling is named explicitly, so an agent must infer the routing.

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 a crisp decision rule for the two modes — include `id` to update, omit it to create — which is the single most important routing decision for this tool. It stops there: no guidance on prerequisites (a creative must already exist via upload_image_creative), no exclusions against sibling ad-creation tools, and no note about when to prefer a different ad format.

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