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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety and repeatability profile is covered elsewhere. The description adds genuinely useful non-annotation context: the cost (1 credit) and the returned field set. It says nothing about failure behavior (e.g., unresolvable handle) or rate limiting, leaving it adequate rather than 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?

Two short sentences: the return payload is front-loaded, followed by the input contract and cost. No filler, though the opening is a telegraphic noun phrase rather than a statement of the action.

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 usefully compensates by enumerating the returned fields, and annotations carry the safety profile. The only material gap is the absence of when-to-use routing against the many sibling tools, which for a one-parameter read is a minor omission.

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% and the single parameter is fully documented in the schema. The description restates the accepted forms (handle, channel ID, URL) without adding format examples or precedence rules, so it neither compensates for nor exceeds the schema — the baseline 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 the resource (a YouTube channel) and enumerates the specific fields returned (title, handle, subscriber and video counts, country, links, tabs), so an agent knows exactly what comes back. It is clear but does not explicitly contrast itself with channel-adjacent siblings such as get_channel_videos or search_youtube.

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 guidance on when to use this tool versus alternatives like search_youtube (to find a channel) or get_channel_videos (for a channel's uploads). The stated input formats (handle, ID, URL) are schema semantics, not usage routing, so the agent must infer selection on its own.

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