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

With no annotations, the description must carry the behavioral burden, and it does disclose two concrete traits: a cost of 1 credit and the required Authorization: Bearer <api_key> header. It still omits error behavior, pagination/rate limits, and whether the target must be public, so it is useful but incomplete.

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?

Front-loaded with the purpose in the first clause, then metadata (platform/resource, cost, auth) in compact form. A stray double period ("author..") is a minor cosmetic flaw but nothing 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 single-parameter fetch tool with no output schema, the description names the returned data (caption, stats, author), plus cost and auth requirements. It is nearly complete; only failure modes and output structure detail are absent, which is acceptable given the tool's simplicity.

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?

The single url parameter is fully documented in the schema (100% coverage, with an example), so the schema does the heavy lifting. The description adds only that the URL should point to a TikTok video, which is consistent but marginally additive; 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?

States a specific verb ("Fetch") and resource (public TikTok video details from a URL) and enumerates the returned fields (caption, stats, author). This clearly separates it from list-oriented siblings like tiktok_posts, though it never names an alternative explicitly.

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?

Usage is implied by the phrase "for a TikTok video URL," so the agent can infer this is the single-post fetch tool. However, there is no explicit when-to-use versus tiktok_posts/tiktok_search guidance and no statement of prerequisites beyond the auth line.

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