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

Annotations already declare read-only, idempotent, open-world behavior. The description adds a meaningful operational caveat: search is not market-filtered and country data requires method=detail, with a tested-date note. It does not cover rate limits or pagination, but the schema handles paging.

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?

The description is front-loaded with purpose and the method list, followed by a useful global-search caveat and two examples. The caveat is somewhat detailed but earns its place by preventing a market-filtering mistake.

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?

With a full input schema, an output schema, and rich annotations, the description supplies the remaining method-selection and global-search context needed to invoke correctly. Nothing material is missing for correct use.

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%, so the schema already documents all 7 parameters, including the method enum meanings. The description's examples illustrate method/keyword/period and method/id, but add little semantic detail beyond the schema; baseline 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?

The description names the resource ('TikTok's library of top-performing ads') and enumerates four specific modes (search, detail, analysis, similar), so the agent knows the tool's scope. It does not explicitly distinguish this tool from sibling tools such as video_search or hashtag_search, so it falls short of a 5.

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 method-level routing ('search by keyword', 'check countries with method=detail') and worked examples, plus a caveat that search is worldwide. It stops short of naming sibling alternatives or explicit when-not-to-use conditions, so it is clear but not exhaustive.

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