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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely new behavior: a stated cost of 1 credit and the framing that results reflect the platform's own perception rather than measured volume. It omits anything about the shape or size of the returned list.

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?

Four short sentences, front-loaded with the core definition, then interpretation, then use case, then cost. The opening 'Search suggestions.' is mildly redundant with the title but nothing else 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 two-parameter read-only lookup with no output schema and annotations covering safety, the description supplies purpose, interpretation, use case, and cost — enough to call it correctly. Only the return format and cache_max_age remain unaddressed.

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 coverage is 50%: query is documented as 'Partial search term' and the description reinforces that with 'partial query'. The second parameter, cache_max_age, is undocumented in both the schema and the description, so no compensation is offered for the gap; baseline 3 fits.

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?

'TikTok's typeahead completions for a partial query' is a precise verb+resource statement that distinguishes this from full-search tools and from siblings like tiktok_hashtag or tiktok_shopSearch. It stops short of naming an alternative but the resource is unmistakable.

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?

'Useful for keyword research' supplies a use context, but there is no when-not guidance, no mention of prerequisites, and no routing to contrasting siblings such as youtube_searchTypeahead or tiktok_hashtag.

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