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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful behavior: the 1-credit cost and the fact that only public videos are supported. It omits what happens for private/deleted posts or rate limits, so it adds value but is not rich.

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, front-loaded sentences with no wasted clauses, though the opening 'Post.' merely repeats the tool name and could be dropped or merged into the following 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?

With no output schema, the description does the right thing by naming the returned metrics. For a simple read-only single-item fetch, the only real gap is the undocumented cache_max_age parameter and edge-case behavior for inaccessible posts.

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 only 50%: the url parameter is documented in the schema, but cache_max_age is undocumented in both schema and description. The description gives no syntax or format hints beyond what the schema already provides, so it fails to compensate for the coverage gap.

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 states a specific resource ('A single public Kwai video') and enumerates what it returns (view, like, comment, forward counts), which distinguishes it from kwai_profile and kwai_userPosts. The leading 'Post.' is redundant with the title, but the rest is clear.

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 implies usage via 'single public' (suggesting private videos are out of scope) but never names an alternative sibling or states when to prefer it over kwai_userPosts or kwai_profile. The credit cost is mentioned, but no when-to-use or when-not-to-use guidance is given.

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