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

Annotations already establish read-only, idempotent, open-world behavior, and the description adds context the annotations cannot express: 1 credit per call, a 20-post cap per response, the exact fields returned, and a concrete failure mode for trial keys. That is solid disclosure, though it stops short of saying how to page past 20 results or whether results are ranked when search_type defaults to Top.

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 short sentences, each carrying a distinct payload: what it searches, what a call returns and costs, and who is allowed to call it. The most decision-relevant information (purpose) is front-loaded and nothing is repeated.

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 no output schema, the description correctly shoulders the burden by listing the returned fields (text, author, likes, reposts, replies, timestamps) and the per-call cap. Two pieces an agent still needs are absent: how to continue past 20 posts, and what 'Top' versus 'Latest' actually changes about results.

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 query, cursor, and search_type are already documented at the schema level, which sets the baseline at 3. The description's phrase "by keyword" loosely reinforces the query parameter and the 20-post cap hints that further calls are needed, but it adds no format, syntax, or cursor-usage detail beyond the schema.

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 opens with a specific verb and resource ("Search X posts by keyword") and names the platform explicitly, which separates it from the tiktok_search and tiktok_videos siblings without needing to open a schema. An agent can pick this tool from the sibling list on this sentence alone.

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 real access condition (paid plans and pay-as-you-go only; trial keys error because the trial is TikTok only), which is genuinely useful routing guidance. However, it never contrasts this with the siblings it most resembles, x_posts or tiktok_search, so the agent must infer that this is the keyword-search path rather than the feed/profile path.

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