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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely non-obvious behavioral context: the preview is appearance-only and does not prove eligibility to serve, which is a real semantic caveat an agent would otherwise get wrong.

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 paragraphs, front-loaded with what the tool does before the caveat about eligibility. The second paragraph is slightly discursive but each sentence carries a distinct point (appearance-only, not proof of eligibility, adds serving issues).

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?

An output schema exists, so return values need not be spelled out, and annotations cover the safety profile. The description supplies the key behavioral caveat, but its silence on the two input parameters is the one material gap for calling it correctly.

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 0% for two parameters, and the description never mentions ad_id or the optional account parameter. ad_id is inferable from the name, but account's purpose and default behavior are undocumented in both the schema and the description, leaving the agent without compensation for the coverage gap.

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 ('renders how an existing ChatGPT Ads ad looks') and clarifies the additional payload (delivery blockers and review status). It distinguishes itself from a pure rendering tool by stating it does NOT prove eligibility, but it never names the closely-related siblings (chatgpt_ads_details, diagnose_chatgpt_ads_delivery) it could be confused with.

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 a clear use context — this is what 'actually answers why is this not running' — which implies when to reach for it. However, it names no alternatives and gives no when-not-to-use guidance, so the agent must infer its place among chatgpt_ads_status and diagnose_chatgpt_ads_delivery.

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