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

Annotations already disclose readOnlyHint=false, openWorldHint=true, and idempotentHint=false. The description adds genuinely new context beyond them: a daily search quota consumed when results are uncached (a real rate/cost constraint), and an interpretation caveat that public longevity and reach do not prove profitability.

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 tight sentences, front-loaded with purpose before the quota note and the analytical caveat. No words wasted, and the ordering prioritizes what an agent needs to decide whether to call.

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 no explanation, and purpose plus quota are covered. But with 8 parameters at 0% schema coverage and no parameter description anywhere, an agent cannot know what 'query', the date range semantics, 'activeOnly', or 'advertiserId' actually do.

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% across 8 parameters (5 required), so the description carries the entire burden and fails to meet it. It only indirectly suggests the 'source' enum (Meta/TikTok) and constrains 'countries' to supported EU/EEA markets; query, dateFrom, dateTo, brandId, activeOnly, and advertiserId are left entirely undefined.

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?

Specific verb (Search) plus resource (Meta/TikTok public ad libraries) and scope (supported EU/EEA countries). It is clear what the tool returns, though it does not differentiate itself from close siblings like search_advertisers, get_library_ad, or analyze_library_ad.

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?

No when-to-use guidance and no named alternatives, despite several sibling tools operating on the same ad-library domain (analyze_library_ad, save_library_ad, get_library_ad). The daily-allowance sentence hints at cost but does not tell the agent which conditions select this tool over the others.

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