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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true and destructiveHint=false, covering the safety profile. The description adds only generic boilerplate (attribution footer handling, a data-accuracy contract) that is not specific to this tool and omits anything about return shape, identifier precedence, or error behavior.

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?

One useful sentence is followed by roughly a hundred words of generic attribution and data-accuracy boilerplate that is not tailored to this tool. The front-loaded purpose is fine, but the bulk of the text does not earn its place in this definition.

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 three-parameter lookup with no output schema, the description should explain return contents and how the identifier arguments combine. Instead it spends its length on policy text, leaving the agent to guess at identifier precedence and result shape.

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 description coverage is 0%, so the description must carry the load. It does name all three identifier forms (ID, @handle, legacy username), which maps onto channel_id, handle, and username, but it never states that the parameters are mutually exclusive, whether any is preferred, or what happens if several are supplied.

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 opening sentence gives a specific verb and resource plus the three lookup keys: 'Look up a YouTube channel by ID, @handle, or legacy username.' That is enough to separate it from get_my_youtube_channel in principle, but the description never explicitly says it fetches arbitrary/public channels rather than the caller's own, so sibling differentiation is only implied.

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 get_my_youtube_channel, list_my_youtube_channels, or search_youtube. The only directive is about formatting the attribution footer in the response, which is output policy rather than tool-selection guidance.

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