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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so the safety profile is covered. The description adds real context beyond that: it clarifies the data is public ad data rather than the caller's own account, and enumerates the returned fields. It does not mention rate limits or pagination, but this is solid added value over the annotations.

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?

Three tightly written sentences: purpose and audience first, return fields second, sibling disambiguation last. No filler, and the most decision-relevant constraint (public vs own account) is not buried.

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?

No output schema exists, yet the description enumerates the return fields (advertiser, ad copy, CTA, link, platforms, run dates, permalink), and annotations cover the safety profile. Nothing an agent needs to call this correctly is missing.

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%, with defaults and examples already documented for query, status, country, and limit. The description adds no parameter-level syntax or format detail beyond what the schema provides, so the baseline of 3 is appropriate.

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 (Search) and resource (PUBLIC Meta Ad Library for any advertiser), and explicitly scopes it against the meta_ads_* siblings that operate on the caller's own ad account. An agent can distinguish this from meta_ads_list_ads without opening either schema.

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 an explicit use case ('great for competitor and creative research') and names the alternative tool family plus the condition that selects it ('use meta_ads_* tools for that'). When and when-not are both covered.

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