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

Annotations already mark the tool as readOnly, idempotent, and non-destructive. The description adds useful behavioral context by explaining the output is measured as a lift against the channel's own median and includes the number of uploads, making the tool's analytical behavior transparent.

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?

The description is two sentences, front-loaded with what is returned, followed by when to use it. Every part adds value with no redundancy or filler.

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 only one fully described parameter, strong safety annotations, and no output schema, the description adequately explains the tool's scope, benchmark method, and intended use. It doesn't detail output formatting, but the low complexity makes that omission acceptable.

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?

The only parameter, channel, is fully described in the schema with accepted forms (handle, URL, ID, or name), giving 100% schema coverage. The description contributes no additional parameter syntax or nuance, so a baseline score of 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?

The description clearly states what the tool does: it returns title length, duration, posting day, and format as performance lifts relative to a channel's own median, plus upload counts. This is specific and distinguishes it from generic YouTube advice and sibling tools like audit_youtube_channel or get_next_video_brief.

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 explicitly says to use it 'instead of generic YouTube advice' and 'when the question is why some of a channel's videos outperform others.' This gives a clear use case and an implicit exclusion, though it does not name sibling tools as alternatives.

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