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

Annotations already establish read-only and open-world behavior, so the description's added value is the credit cost (1 credit) and the 'public details' scope, which signals no authenticated/private analytics or ownership data. Caching behavior, despite an exposed cache_max_age parameter, is not disclosed.

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?

Two short sentences, front-loaded with the resource and followed by the returned-field summary and cost. The opening 'Channel details' slightly restates the title, but nothing else 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 simple read tool with annotations covering safety, the description supplies the field scope and pricing an agent needs to decide whether to call it. The only real gap is the undocumented optional cache_max_age parameter, which is secondary.

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%: `handle` is documented in the schema while `cache_max_age` is undocumented in both schema and description. The description says nothing about accepted identifier formats or cache semantics, so it does not 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?

States a specific resource (a YouTube channel) and enumerates the returned fields (subscribers, video count, description, links), which implicitly distinguishes it from youtube_channelVideos/channelShorts siblings that return content lists. It never names a sibling explicitly, so an agent must infer the split rather than being told it.

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 only implied by 'Public details' — useful when you need channel metadata before fetching content. There is no when-not guidance and no mention of when to prefer youtube_channelVideos, youtube_channelPlaylists, or youtube_search instead.

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