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

Annotations already establish read-only, idempotent, non-destructive behavior, so the bar is lower. The description adds genuine context: what data is inspected, the qualifier 'where observed' (hinting that some sources may be absent), and that twelve named checks are executed. It does not disclose the six-hour cache, which only appears in the schema, nor the shape of returned findings.

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?

A single dense sentence with the scope front-loaded. It is efficient, though the trailing clause 'twelve checks each naming what it reads' is slightly cryptic and could be tightened.

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 partially compensates by stating what is read and that twelve self-describing checks run. However, it says nothing about how results or findings are returned, and omits the caching behavior that materially affects repeated calls.

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 100%, with both 'v' (video id or URL) and 'fresh' (bypass the six-hour cache) fully documented in the schema. The description adds no parameter-level detail beyond that, so the baseline of 3 applies.

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 names a specific resource and scope: a single YouTube video run against the 'video anchor model', enumerating what is read (metadata, chapters, captions, storyboard). The emphasis on 'One' video implicitly separates it from video_channel and video_site, though neither sibling is named explicitly. Verb is implied by the tool name rather than stated.

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?

There is no explicit when-to-use statement, no prerequisites, and no routing to alternatives among the video_channel / video_site siblings. The only signal is the implicit single-video scope embedded in the purpose sentence.

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