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

Annotations already declare readOnlyHint and openWorldHint, so the description adds real value beyond them: it discloses that no signer/auth is needed, that the data is scraped from the tag page, and that the call costs 1 credit. This is genuine operational context not present in the structured fields.

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, front-loaded with the purpose and then the key operational facts (source, auth, cost). Minimal waste, though 'Hashtag details' slightly duplicates the title and could be merged into the stats sentence.

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 simple read-only stat tool with an annotation-covered safety profile, the description supplies what to expect back, that no auth is required, and the credit cost. Only the undocumented 'cache_max_age' parameter is left unexplained, which is a minor gap.

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%: the required 'hashtag' parameter is well documented in the schema (tag without # or a full /tag/ URL), while 'cache_max_age' is undocumented in both schema and description. The description adds no parameter-level guidance, so at this coverage baseline a 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?

It names a specific resource (a TikTok hashtag) and enumerates the exact payload: total videos, total views, description, and cover image, which implicitly separates it from tiktok_hashtagVideos (videos vs. metadata). It does not name that sibling explicitly, so an agent must infer the boundary from the returned-fields list.

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?

The description gives useful context (reads straight off the tag page, no signer, 1 credit) but never states when to pick this over tiktok_hashtagVideos or what a caller should do with the stats. There are no explicit when-not conditions, so usage is only implied.

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