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

With no annotations provided, the description carries the full burden. It discloses the returned fields and the input exclusivity rule, but does not mention possible errors, rate limits, or side effects. Since it is a read-only operation, this is adequate but not richly 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 exactly two sentences: one listing all output fields, the other stating the input constraint. It is well-structured, front-loaded with the tool's purpose, and contains no redundant or extraneous information.

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?

Though there is no output schema, the description lists all expected return fields, giving the agent a clear picture of the result. It also specifies the input rules. It could be more complete by describing error behavior, but for a simple getter tool it is adequately complete.

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 input schema already documents each parameter with 100% coverage, giving an appropriate baseline of 3. The description adds value by clarifying that id, url, and name are mutually exclusive alternatives ('exactly one of'), which is not explicit in the schema. This improves parameter understanding.

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 uses the specific verb 'Get details' with the resource 'YouTube channel' and enumerates the exact data fields returned (channel name, subscriber count, etc.). This clearly distinguishes it from sibling tools like search_youtube_channels or youtube_video_details.

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 provides an explicit usage constraint: 'Provide exactly one of id, url, or name.' This tells the agent when to use the tool and the required input format. It lacks explicit exclusion of alternatives (e.g., 'use search_youtube_channels to find channels'), but the constraint is clear enough for basic usage.

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